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CHEM 121 Chapter 2 Answers
what is the law of conservation of mass (by Lavoisier)
there is no change in mass when a chemical reaction occurs
What is the law of definite proportions (by Proust)
a compound always contains elements combined in the same proportion by mass Ex 1.000g of water (H2O) .111g of H and .889g of O ratio is always 1:8.01
what is the atomic theory of matter and who discovered it
John Dalton all matter, whether element, compound, or mixture, is composed of small, indivisible particles called atoms. Atoms are the building blocks of matter
what is the first basic postulate of Dalton’s atomic theory
matter is composed of tiny particles called atoms
what is the second basic postulate of Dalton’s atomic theory
all atoms of an element are identical in mass and other properties
what is the third basic postulate of Dalton’s atomic theory
atoms of different elements differ in mass and other properties
what is the fourth basic postulate of Dalton’s atomic theory
compounds are composed of atoms of different elements combined in fixed proportions by mass. The number of atoms of elements in a compound is a small whole number ratio
what is the fifth basic postulate of Dalton’s atomic theory
atoms are indestructible. Atoms are neither created nor destroyed in chemical reactions: simply rearranged to yield new substances
who was a renowned scientist at the same time as Dalton who did not accept his atomic theory
Sir Humphrey Davy
what is the law of multiple proportions
when two elements combine to form more than one compound, the masses of one element that combine with a fixed mass of the other element are in ratios of small whole numbers
whose theory and what theory predicted the law of multiple proportions
Dalton’s atomic theory
what is an atom
the smallest particle of an element that retains the chemical properties of the element
how was the first subatomic particle discovered
phenomenon of an electric discharge in an evacuated glass tube, gas discharge tube (Crookes Tube)
what is a cathode ray tube
crude television tube
cathode emits an invisible ray called
a cathode ray
what does a cathode ray tube look like
on one end there is a cathode then there is a metal shield with a slit then there is a florescent screen that will show the cathode ray then on the other side there is an anode connected on each end is a high voltage source
what did JJ Thomson discover with the cathode ray tube
magnetic and electric fields bend the cathode rays. suggests that they are a basic component of all matter (beam of electrons)
what is the charge to mass ratio of an electron (also discovered by JJ Thomson)
-1.76 x 10^8 C/g (negative because electrons have a negative charge)
what date was the electron discovered
April 1897
who did the oil-drop experiment
Robert Millikan
What was the oil drop experiment?
What was the result of the oil drop experiment
discovering the charge on an electron
what is the charge on an electron
-1.60 x 10^-19 C
what is the mass of an electron
9.09 x 10^-28 g
who discovered that cathode rays caused some materials to emit rays
Rontgen
what were the rays called that Rontgen discovered
x-rays
who discovered that some compounds emitted rays spontaneously without cathode ray stimulation
Becquerel
what did Becquerel’s discovery suggest
radioactivity
what other scientist also worked with Becquerel to discover radioactivity
Marie Curie
who discovered that there are three types of rays produced by radioactivity
Ernest Rutherford
what were the three types of rays that Rtherford discovered
1. Alpha rays: beams of positively charged particles 2. Beta rays: beams of negatively charged particles 3. gamma rays: high energy radiation; no charge
who came up with the plum pudding model
JJ Thomson
what did the plum pudding model look like
a uniform sphere of positively charged matter with negatively charged electrons embedded in it
what did Rutherford, Geiger, and Marsden look at
the scattering angles of alpha beams when it passed through thin gold foil
what unexpectedly happened in the gold foil experiment
some of the particles had large scattering angles and even bounced back
what was expected to happen with the gold foil experiment
the alpha particles would have small scattering angles because of the plum pudding model
what did Rutherford’s new model of the atom look like
the atom has two distinct parts; a nucleus with positively charges particles and negatively charged particles surround the nucleus but are far removed. The atom is mostly empty space
what are the three subatomic particles that an atom is composed of
protons, neutrons, and electrons
what is the charge on a proton and where is it located
positive charge and in the nucleus
what is the charge on a neutron and where is it located
neutral charge and in the nucleus
what is the charge on an electron and where is it located
negative charge and far removed from the nucleus
who discovered protons and when
Rutherford in 1911
who discovered neutrons and when
James Chadwick in 1932
what is the charge and mass of an electron
-1.60 x 10^-19 C 9..109 x 10^-28 g
what is the charge and mass of a proton
1.60 x 10^-19 C 1.673 x 10^-24 g
what is the charge and mass of a neutron
0 C 1.675 x 10^-24 g
atoms are electrically neutral because
number of protons is equal to the number of electrons
all of an atom’s mass is found in
the nucleus
what characterizes and element and who came up with this method
the number of protons Henry Moseley 1913
what is the atomic number
number of protons, identifies the element-chemical identity
what is the mass number for an atom
the total number of protons and neutrons for the atom
what is an isotope
when an atom of a certain element has different numbers if neutrons. Ex. carbon can have 7 or 8 neutrons
what does the number of neutrons affect
the mass of the atom
what it the nucleus of a specific isotope called
nuclide
chemical symbol for atom (know this)
what are four important radioactive isotopes and what are they used for
1. Cobalt-60: cancer radiation therapy 2. Cesium-137: food sterilization (as cesium ion) 3. iodine-129: thyroid radiation therapy (as NaI) 4. technetium-99: medical imagining of internal organs
who discovered isotopes
JJ Thomson
what was the discovery of isotopes in conflict with
Dalton’s atomic theory (postulate 2)
how was Dalton’s atomic theory modified after isotopes were discovered
all atoms of a given element have the same number if protons and chemical properties
what is the mass number equal to
number of protons + number of neutrons
the number of protons is equal to
the number of electrons
in the nineteenth century scientists recognized that some elements
have very similar chemical properties
what did Mendeleev and Meyer do
arranged elements by increasing atomic number in a horizontal row. then elements with similar properties were arranged in columns called groups. this became the periodic table
what are the three categories for elements
metals, nonmetals, and metalloids
where are metals located on the periodic table
left and center
what are characteristics of metals
good conductors of heat and electricity, luster, ductile, malleable, and solid at room temp (except mercury)
where are nonmetals located in there periodic table
to the right
what are characteristics of nonmetals
opposite of metals. poor conductors of heat and electricity, brittle, and dull surface
where are metalloids located on the periodic table
right-center
what are characteristics of metalloids
intermediate between metals and nonmetals
of the three categories of elements, what category do most elements fall into
metals
what are the two major groups for the periodic table
group A: representative or main group elements group B: transition (metal) elements
what are the groups with special names on the periodic table and what are their names
1A: alkali metals (not H) 2A: alkaline earth metals 6A: chalcogens 7A: halogens 8A: noble (rare) gases
how do elements in group 8A (noble gases) exist
as free, single atoms
how do most elements exist
as molecules or ions
what are the two ways that atoms combine
1. by sharing electrons to make molecules 2. by transferring electrons to yield ions and making ionic compounds
how are molecules formed
by the combinations of nonmetals with nonmetals or metalloids, they have definitely proportion and are neutral
what are important nonmetallic molecules (diatomic molecules)
H2, O2, N2, F2, Cl2 (gases at room temp) Br2 (liquid at room temp) I2 (solid at room temp)
what does it mean if a molecule is a diatomic molecule
it is made up of two atoms
what are the two elemental forms of oxygen
O2 and O3
what are O2 and O3 called
allotropes
what is an allotrope
different forms of an element Ex. oxygen has two, carbon has four
what are the different types of molecular compounds
1. diatomic molecular compounds (HCl, CO) 2. polyatomic molecular compounds (CO2, NH3, H2O) 3. polyatomic molecular compounds with a metalloid (SiO2, SiH4)
what is an ion
species containing a net charge by either gaining electrons (negative charge) or by losing electrons (positive charge)
what is a cation
positively charges ion, attracted to the negative cathode in an electrolytic cell
what is an anion
negatively charged ion, attracted to the positive anode in an electrolytic cell
when metals become ions they tend to
lose electrons (cations)
when nonmetals become ions they tend to
gain electrons (anions)
what is a monatomic ions
and ion with only one atom, metals and nonmetals
monatomic metal ions are
cations Ex. Na+, Ca2+, K+, Mg2+
monatomic nonmetal ions are
anions Ex. F-, Cl-, O2-, N3-
how do you predict the charges for the atoms in groups 1A and 2A
they will lose the same amount of electrons as their group number
how do you predict the charges for atoms in groups that are not 1A or 2A
the number of electrons that they will GAIN is equal to 8 minus the group number Ex. group 7A: 8-7=1 so they will gain one electron
Relative atomic masses
based on known masses. example is carbon which is 12 times that of hydrogen
what is the unit that is used to express the mass of atoms/molecules/formula units
amu (atomic mass unit)
how do atomic mass units work
they are almost whole numbers always. for example carbon has 12 amu
what is a mole
6.022 x 10^23 SI base unit for amount of a substance
actual definition of a mole
the amount of matter that contains as many elementary units (atoms, molecules, etc) as there are atoms in exactly 12 g of C-12 Basically: 1 mole C-12 = 6.022 x 10^23 atoms = 12.000 g
what is molar mass
mass (g) of one mole of a substance, numerically equivalent to atomic mass in amu
how to convert between mass, moles, and number of atoms
– mass —-> moles need molar mass – moles —-> atoms need Avogadro’s number – this can be done the other way too
CHEM 121 Chapter 3 Answers
Electromagnetic Radiation
radiation type/spectrum in which electric and magnetic fields vary simultaneously.
Electromagnetic Waves
a form of energy that travels through space (in the shape of a wave)
Amplitude
height of a wave (from origin to crest)
Wavelength
(aka lambda) distance between two corresponding parts of a wave
Frequency
the number of completed waves within a given amount of time
Speed of Light
3.00 x 10^8 m/s
Interference Patterns
occur when waves from different sources arrive at the same point at the same time
Line Spectra
the emission of light only at specific wavelengths
Continuous Spectra
an emission spectrum that consists of a continuum of wavelengths
nanometers to meters
10^-9
hertz to kilohertz
10^-2
Units for Frequency
Hertz (Hz)
Units for Wavelength
meters (m)
Units for Energy
Joules (J)
Photon
a particle of light
Endothermic Reaction
absorbs photons, increases energy
Exothermic Reaction
releases photons, decreases energy
Wave-Particle Duality
electrons and light can behave as both a wave and a particle
Blackbody Radiation
emission of light from hot objects
c = λv
speed of light = wavelength x frequency
The Photoelectric Effect
refers to the emission of electrons from a metal when light shines on the metal
E = hc/λ (simplified: E = 1.24/λ)
energy equals planck’s constant times speed of light over wavelength
Line Spectra
emission of light only at specific wavelengths; every element has its own unique emission spectrum (ex: neon signs)
The Bohr Model
model of the atom in which electrons move rapidly around the nucleus in paths called orbits, violation of classical physics since the electron acts like a stationary wave not a particle like previously thought
Emission of light from an atom occurs when an electron
drops from a higher to a lower energy level
Absorption of light from an atom occurs when an electron
rises from a lower to higher energy level
Ground State Electron Configuration
lowest energy configuration, the most likely state since matter is most stable at its lowest energy level
Excited State Electron Configuration
a higher energy arrangement of electrons in an atom that occurs when an electron rises to a higher energy level
The deBroglie Equation
wavelength = h/mv
Heisenburg Uncertainty Principle
it is impossible to know exactly both the velocity and the position of a particle at the same time, (formula?)
Quantum Mechanical Model of the Atom
an atomic model in which electrons are treated as waves
Principle Quantum Number
symbolized by n, indicates the main energy level occupied by the electron
Atomic Orbital
the probability of finding an electron at various locations in the region of space around the nucleus
Angular Momentum Number
symbolized by l, indicates the shape of the orbital
Values of L
0 to (n-1) are possible within one orbital
Magnetic Quantum Number
symbolized by m, indicates the orientation of an orbital around the nucleus
Degenerate Orbital
a group of orbitals with the same energy
Spin Quantum Number
the quantum number that describes the rotation/momentum of the orbital
Values of the Spin Quantum Number
+1/2, -1/2
The Pauli Exclusion Principle
no two electrons in the same atom can have the same set of four quantum numbers
Hund’s Rule
electrons must have the same spin before pairing occurs (to make sure ones of the same spin are properly present)
The Aufbau Principle
states that each electron occupies the lowest energy orbital available
Core Electrons
electrons found in the inner shells (not valence)
Valence Electrons
electrons in the outermost shell
Periodic Group
vertical columns of elements on the periodic table that share similar properties
Metal Elements
elements on the left hand side of the periodic table
Non-Metal Elements
elements on the right hand side of the periodic table
Metalloid Elements
B, Si, Ge, As, Sb, Te, Po
Noble Gases
elements in group 18 of the periodic table. have no charge and are gases under normal conditions. used in abbreviations of electron configuration (Helium, Neon, Argon, Krypton, Xenon, Radon)
Main Group Elements
elements in the s-block or p-block of the periodic table
Transition Metals
groups 3-12 on the periodic table
Halogens
group 17 on the periodic table
Alkali Metals
group 1 of the periodic table
Alkaline Earth Metals
group 2 of the periodic table
Abbreviated Electron Configuration
[matching noble gas config] then the remainder of electrons
Effective Nuclear Charge (Zeff)
the actual nuclear charge experienced by an electron, defined as the charge of the nucleus plus the charge of the shielding electrons
How Does Ion Size Compare to Parent Atom Size?
a cation is smaller due to it having the same protons/neutrons as the parent but less electrons, an anion ??
Isoelectronic Series
a series of atoms, ions, or molecules having the same number of electrons
Ionization Energy
the energy required to remove an electron from the current outermost shell (IE1, the valence, IE2 from a cation, etc.) which creates a cation
Electron Affinity
the energy change that occurs when an electron is gained by a neutral atom
Covalent Radius
one-half the distance between the nuclei of two identical atoms when they are joined by a covalent bond
Horizontal Trend in Atomic Radius
left to right, increase in size
Vertical Trend in Atomic Radius
upper to lower, increase in size
Electron Shielding
core electrons shield valence electrons from full charge of the nucleus
L Value Order of Increase
s < p < d < f
S Orbital
l = 0, 2 possible electrons
P Orbital
l = 1, 6 possible electrons
D Orbital
l = 2, 10 possible electrons
F Orbital
l = 3, 14 possible electrons
1 Hertz (s^-1) =
1000 kHz
What Are the 3 Steps of Predicting a Configuration of Electrons?
1. find the element’s atomic number which is equal to its number of electrons 2. draw the diagram to figure out how the shells will fill to accommodate that number 3. write out the configuration properly 4. abbreviate the config if needed by repeating the process
Helium Electron Configuration
1s2
Neon Electron Configuration
1s2 2s2 2p6
Argon Electron Configuration
1s2 2s2 2p6 3s2 3p6
Krypton Electron Configuration
1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6
How Do You Determine the Order in Which Electron Shells Are Filled?
The Aufbau Model (aka ‘building up’ by following a map)
Calculate Energy from Frequency
E = hv
Calculate Wavelength from Energy
λ = hc/E
Types of Electromagnetic Radiation
radio waves, microwaves, infrared radiation, (visible light), UV radiation, X-Rays, gamma rays
Periodic Law
the physical and chemical properties of the elements are all periodic functions of their atomic numbers and are thus organized by those atomic numbers
Why Are Atomic Masses for Some Elements Given in Brackets?
the isotopes of those elements are unstable (radioactive decay affects mass)
Monatomic Ion
an ion formed from a single atom
Polytomic Ion
a positively charged; covalently bonded group of atoms
Ionic Bonds (Parasitic)
formed when electrons are transferred from one atom to another
Covalent Bonds (Symbiotic)
created by sharing electrons with other atoms.
Ionic Compound
a compound composed of positive and negative ions
Molecular Compound
a compound that is composed of molecules
Chemical Formulas
tells what elements make up a compound and the ratios of the atoms of those elements
How Do Ionic Compounds Form?
when a neutral atom transfers one or more electrons to another atom, it results in the formation of an ionic compound
How Do Covalent Compounds Form?
by sharing electrons
Electronegativity
the ability of an atom to attract electrons when the atom is in a compound
Pure Covalent Bonds
equal sharing of electrons
Polar Covalent Bonds
unequal sharing of electrons
Hydroxide Formula
OH-
Cyanide Formula
CN-
Phosphate Formula
PO4 3-
Nitrate Formula
NO3-
Carbonate Formula
CO3 2-
Bicarbonate Formula
HCO3-
Sulfate Formula
SO4 2-
Ammonia Formula
NH3
Metallic Elements Make
cations
Nonmetallic Metals Make
anions
What Two Types of Elements Are Required for an Ionic Bond?
A metal (cations) and a non-metal (anions)
the total number of positive charges in an ionic compound must equal
the total number of negative charges
A Cation’s Charge is Equal To
The Group # (+)
The Charge of Group 13-17 Cations is Equal To
The Group # minus 10
Cation Charges Are
positive
Anion Charges Are
negative
Bond Type With Zero Electronegativity Difference
Pure Covalent, < 0.4 difference
Bond Type With Intermediate Electronegativity Difference
Polar Covalent, 0.4 to 1.8 difference
Bond Type With Large Electronegativity Difference
Ionic, >1.8 difference
NaCl
sodium chloride
KBr
potassium bromide
CaI2
calcium iodide
CsF
cesium fluoride
LiCl
lithium chloride
Na2O
sodium oxide
Mg3N2
magnesium nitride
Ca3P2
calcium phosphide
Al4C3
aluminum carbide
KC2H3O2
potassium acetate
NaHCO3
sodium bicarbonate
Al2(CO3)3
aluminum carbonate
NH4Cl
ammonium chloride
CaSO4
calcium sulfate
Mg3(PO4)2
magnesium phosphate
FeCl2
Iron (II) Chloride
FeCl3
Iron (III) Chloride
Hg2O
mercury (I) oxide
HgO
mercury (II) oxide
SnF2
tin (II) flouride
SnF4
tin (IV) flouride
Variable Charge
when a metal can form two or more types of ions with different charges, transition metals
Hydrates
compounds that have a specific number of water molecules attached to them
SO2
sulfur dioxide
SO3
sulfur trioxide
NO2
nitrogen dioxide
N2O4
dinitrogen tetroxide
N2O5
dinitrogen pentoxide
BCl3
boron trichloride
SF6
sulfur hexafluoride
PF5
phosphorus pentafluoride
P4O10
tetraphosphorus decoxide
IF7
iodine heptafluoride
E = hv = hc/λ
to convert energy between/using wavelength and frequency
Megahertz (MHz)
1 x 10^6 Hz
Convert MHz fo Hz
1×10^6/1
the higher the wavelength the
lower the energy
N Cannot be Equal to
When Naming an Ionic Compound Formula
list the cation first, do not use prefixes, change the suffix to ide
chem 121 Chapter 4 Answers
For representative elements, valence electrons are those electrons located A) closest to the nucleus. B) in the outermost subshell. C) in the outermost shell. D) in s orbitals.
C) in the outermost shell.
How many electrons appear in the Lewis symbol for an element whose electron configuration is 1s 2 2s 2 2p 4 ? A) 2 B) 4 C) 6 D) 8
C) 6
Elements in groups IA and IIIA of the periodic table possess, respectively, how many valence electrons? A) 1 and 1 B) 1 and 3 C) 3 and 1 D) 8 and 8
B) 1 and 3
The “octet rule” relates to the number eight because A) only atoms with 8 valence electrons undergo chemical reaction. B) ions with charges of +8 and -8 are very stable. C) atoms, during compound formation, frequently obtain 8 valence electrons. D) all electron subshells can hold 8 electrons.
C) atoms, during compound formation, frequently obtain 8 valence electrons.
Formation of a positive ion is the result of an atom A) losing one or more protons. B) losing one or more electrons. C) gaining one or more protons. D) gaining one or more electrons.
B) losing one or more electrons.
How many total electrons are present in a N 3- ion? A) 4 B) 7 C) 10 D) 12
C) 10
Elements in groups IIA and VIIA of the periodic table would, respectively, be expected to form ions with charges of A) +2 and +7 B) -2 and -7 C) +2 and +1 D) +2 and -1
D) +2 and -1
Which of the following ions is not isoelectronic with the noble gas xenon? A) Cs + B) I – C) Sn 4+ D) Sb 3-
C) Sn 4+
The correct formula for the ionic compound containing Ga 3+ and Te 2- ions would be A) GaTe B) Ga 3 Te 2 C) Ga 2 Te 3 D) Ga 2 Te
C) Ga 2 Te 3
The correct formula for the ionic compound formed between Na and N is A) Na 3 N B) NaN 3 C) Na 2 N 3 D) Na 3 N 2
A) Na 3 N
In which of the following ionic compounds are ions with a +1 charge present? A) Cs 2 Te B) Ga 2 Te 3 C) Be 2 Si D) CaS
A) Cs 2 Te
In which of the following pairs of compounds are both members of the pair ionic compounds? A) NF 3 and HI B) Na 2 Se and NF 3 C) KBr and H 2 Se D) KCl and ZnO
D) KCl and ZnO
Which of the following statements is an accurate description of the structure of the ionic compound NaBr A) alternating layers of Na and Br atoms are present B) alternating layers of Na + and Br – ions are present C) individual molecules containing a Na + and Br – ion are present D) each cation present is surrounded by six anions in an extended array
D) each cation present is surrounded by six anions in an extended array
The correct name for the ionic compound Al 2 Se 3 is A) aluminum selenide B) aluminum(III) selenide C) aluminum triselenide D) dialuminum triselenide
A) aluminum selenide
The correct name for the ionic compounds V 2 Se 3 is A) vanadium selenide B) vanadium(III) selenide C) vanadium triselenide D) divanadium triselenide
B) vanadium(III) selenide
The Roman numeral (III) in the name manganese(III) oxide indicates that A) there are three times as many manganese atoms present as oxygen atoms B) there are three manganese atoms per formula unit C) there are three oxygen atoms per formula unit D) manganese is present in the form of +3 ions
D) manganese is present in the form of +3 ions
Which of the following compounds contains 4 atoms per formula unit? A) vanadium(III) nitride B) lead(II) iodide C) calcium iodide D) iron(III) chloride
D) iron(III) chloride
Which of the following statements about polyatomic ions is correct? A) all have names which end in -ate B) all must contain oxygen C) they must contain more than one atom and be charged D) all carry a charge of negative one
C) they must contain more than one atom and be charged
The formulas of the sulfate ion, the nitrate ion, and the phosphate ion are, respectively, A) SO 3 2- , NO 3 2- , PO 3 2- B) SO 4 2- , NO 4 2- , PO 4 2- C) SO 4 2- , NO 3 – , PO 4 2- D) SO 4 2- , NO 3 – , PO 4 3-
D) SO 4 2- , NO 3 – , PO 4 3-
Which one of the following compounds has a formula which contains parentheses? A) strontium carbonate B) lithium nitrate C) barium hydroxide D) ammonium nitrate
C) barium hydroxide
For which of the following elements is the listed number of valence electrons correct? A) Al – 3 valence electrons B) Cl – 5 valence electrons C) Si – 2 valence electrons D) more than one correct response E) no correct response
A) Al – 3 valence electrons
Which of the following elements would have a Lewis symbol that contains 5 electrons? A) nitrogen B) fluorine C) phosphorus D) more than one correct response E) no correct response
D) more than one correct response
In which of the following pairs of ions do both members of the pair contain the same total number of electrons? A) S 2- and Cl – B) Na + and K + C) Al 3+ and N 3- D) more than one correct response E) no correct response
D) more than one correct response
Which of the following elements would be expected to form a monoatomic ion with a charge of +2? A) oxygen B) sulfur C) magnesium D) more than one correct response E) no correct response
C) magnesium
In which of the following pairings is the chemical formula not consistent with the ions shown? A) M 2+ , X 3- , M 3 X 2 B) M 2+ , X – , MX 2 C) M + , X 3- , MX 3 D) more than one correct response E) no correct response
C) M + , X 3- , MX 3
Which of the following is an incorrect statement about the number of electrons lost or gained by a representative element during ion formation? A) The number is usually 3 or less. B) The number is governed by the octet rule. C) The number is related to the position of the element in the periodic table. D) more than one correct response E) no correct response
E) no correct response
The mechanism for ionic bond formation always involves the transferring of A) electrons from nonmetallic atoms to metallic atoms. B) protons from the nucleus of metallic atoms to the nucleus of nonmetallic atoms. C) sufficient electrons to produce ions of equal but opposite charge. D) more than one correct response E) no correct response
E) no correct response
In which of the following pairs of ionic compounds do both members of the pair contain +1 ions? A) KCl and CaO B) Na 3 N and Li 2 S C) AlCl 3 and MgF 2 D) more than one correct response E) no correct response
B) Na 3 N and Li 2 S
In the formation of which of the following ionic compounds is the number of electrons transferred per formula unit equal to three? A) AlN B) K 3 N C) BaCl 2 D) more than one correct response E) no correct response
D) more than one correct response
Which of the following pairings of compound name and compound formula is incorrect? A) sodium oxide – Na 2 O B) magnesium sulfide – MgS 2 C) potassium chloride – KCl D) more than one correct response E) no correct response
B) magnesium sulfide – MgS 2
Which of the following ionic compounds would have a name that contains the Roman numeral III? A) AlCl 3 B) FeBr 3 C) Cu 3 N D) more than one correct response E) no correct response
B) FeBr 3
In which of the following compounds is there a one-to-two ratio between positive and negative ions? A) calcium sulfide B) magnesium bromide C) lead(IV) oxide D) more than one correct response E) no correct response
D) more than one correct response
In which of the following pairs of polyatomic ions do both members of the pair have the same charge? A) sulfate and phosphate B) carbonate and hydroxide C) ammonium and nitrate D) more than one correct response E) no correct response
E) no correct response
Which of the following pairings of compound name and compound formula is incorrect? A) sodium acetate – NaC 2 H 3 O 2 B) barium sulfate – BaSO 4 C) magnesium nitrate – MgNO 3 D) more than one correct response E) no correct response
C) magnesium nitrate – MgNO 3
Which of the following compounds contain more than 10 atoms per formula unit? A) ammonium phosphate B) aluminum carbonate C) iron(III) cyanide D) more than one correct response E) no correct response
D) more than one correct response
(1) Representative elements in the same group of the periodic table have the same number of valence electrons. (2) Discrete molecules do not exist in ionic compounds. (3) A sulfate ion has one less oxygen than a sulfite ion. A) All three statements are true. B) Two of the three statements are true. C) Only one of the statements is true. D) None of the statements is true.
B) Two of the three statements are true.
(1) All ionic compounds which contain metal ions have names which contain Roman numerals. (2) Ionic compounds tend to have high melting points and be good conductors of electricity when in the molten state. (3) Three ions are present in one formula unit of a compound that contains Na + and O 2- ions. A) All three statements are true. B) Two of the three statements are true. C) Only one of the statements is true. D) None of the statements is true.
B) Two of the three statements are true.
(1) If an atom loses one or more electrons, it becomes negatively charged because protons now outnumber electrons. (2) Nitrogen, a group VA element, possesses 5 valence electrons. (3) Polyatomic ions are generally not very stable and usually lose their identity during chemical reactions. A) All three statements are true. B) Two of the three statements are true. C) Only one of the statements is true. D) None of the statements is true.
C) Only one of the statements is true.
(1) An atom with the electron configuration 1s 2 2s 2 2p 2 possesses two valence electrons. (2) The formula of the ionic compounds that contains Ba 2+ and N 3- ions is Ba 2 N 3 . (3) The polyatomic ions nitrate and azide are both tetraatomic entities. A) All three statements are true. B) Two of the three statements are true. C) Only one of the statements is true. D) None of the statements is true.
D) None of the statements is true.
(1) Ionic bonds result from the sharing of one or more pairs of electrons. (2) The compound copper(II) phosphate contains eight oxygen atoms per formula unit. (3) Ionic compounds which contain fixed charge metals cannot contain polyatomic ions. A) All three statements are true. B) Two of the three statements are true. C) Only one of the statements is true. D) None of the statements is true.
C) Only one of the statements is true.
(1) The number of valence electrons possessed by an atom can never exceed four. (2) Binary ionic compounds containing two nonmetals do not occur. (3) The name of the ionic compounds Cu 2 S is copper(II) sulfide. A) All three statements are true. B) Two of the three statements are true. C) Only one of the statements is true. D) None of the statements is true.
C) Only one of the statements is true.
(1) Hydrogen carbonate and bicarbonate are two names for the same polyatomic ion. (2) The symbol for an atom of X that has lost two electrons is X 2-. (3) In all ionic compounds the total charge of the ions present per formula unit must add up to zero. A) All three statements are true. B) Two of the three statements are true. C) Only one of the statements is true. D) None of the statements is true.
B) Two of the three statements are true.
(1) The octet rule is used to determine the number of valence electrons an atom possesses. (2) The formula for the compound sodium carbonate contains parenthesis. (3) Group IIA and VIA elements form ions which carry two units of charge. A) All three statements are true. B) Two of the three statements are true. C) Only one of the statements is true. D) None of the statements is true.
C) Only one of the statements is true.
(1) Calcium sulfide is a compound in which both types of ions present have the same electron configuration, that of the noble gas argon. (2) The charge on the positive ions present in the compound Al 2 S 3 is +3. (3) The polyatomic ions ammonium and cyanide do not contain oxygen. A) All three statements are true. B) Two of the three statements are true. C) Only one of the statements is true. D) None of the statements is true.
A) All three statements are true.
(1) The most abundant ion in hard water is usually Na + . (2) Fresh water purified for drinking purposes contains no ions. (3) Tooth enamel contains both monatomic and polyatomic ions. A) All three statements are true. B) Two of the three statements are true. C) Only one of the statements is true. D) None of the statements is true.
C) Only one of the statements is true.
1s 2 2s 2 2p 6 3s 1 a) 1 valence electron b) 3 valence electrons c) 5 valence electrons d) 7 valence electrons
a) 1 valence electron
1s 2 2s 2 2p 6 3s 2 3p 5 a) 1 valence electron b) 3 valence electrons c) 5 valence electrons d) 7 valence electrons
d) 7 valence electrons
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p3 a) 1 valence electron b) 3 valence electrons c) 5 valence electrons d) 7 valence electrons
c) 5 valence electrons
Group VA element a) 1 valence electron b) 3 valence electrons c) 5 valence electrons d) 7 valence electrons
c) 5 valence electrons
Lewis symbol is . . : X : . a) 1 valence electron b) 3 valence electrons c) 5 valence electrons d) 7 valence electrons
c) 5 valence electrons
M2+ and X- a) MX b) M2X c) MX2 d) M2X3
c) MX2
M3+ and X2- a) MX b) M2X c) MX2 d) M2X3
d) M2X3
M2+ and X2- a) MX b) M2X c) MX2 d) M2X3
a) MX
M has 2 valence electrons and X has 7 valence electrons a) MX b) M2X c) MX2 d) M2X3
c) MX2
M is a group IIIA element and X is a groups VIA element a) MX b) M2X c) MX2 d) M2X3
d) M2X3
-2 monoatomic ions are present. a) K3N b) AlF3 c) CaSO4 d) (NH4)2S
d) (NH4)2S
+1 monoatomic ions are present. a) K3N b) AlF3 c) CaSO4 d) (NH4)2S
a) K3N
Positive and negative ions present carry the same amount of charge. a) K3N b) AlF3 c) CaSO4 d) (NH4)2S
c) CaSO4
More negative ions are present than positive ions. a) K3N b) AlF3 c) CaSO4 d) (NH4)2S
b) AlF3
Two ions are present per formula unit. a) K3N b) AlF3 c) CaSO4 d) (NH4)2S
c) CaSO4
Contains the elements nitrogen and hydrogen a) hydroxide ion b) ammonium ion c) nitrate ion d) sulfate ion
b) ammonium ion
Contains three oxygen atoms a) hydroxide ion b) ammonium ion c) nitrate ion d) sulfate ion
c) nitrate ion
contains a total of four atoms a) hydroxide ion b) ammonium ion c) nitrate ion d) sulfate ion
c) nitrate ion
contains one hydrogen atom a) hydroxide ion b) ammonium ion c) nitrate ion d) sulfate ion
a) hydroxide ion
has a negative two charge a) hydroxide ion b) ammonium ion c) nitrate ion d) sulfate ion
d) sulfate ion
Sodium oxide a) two atoms per formula unit b) three atoms per formula unit c) four atoms per formula unit d) five or more atoms per formula unit
b) three atoms per formula unit
Calcium chloride a) two atoms per formula unit b) three atoms per formula unit c) four atoms per formula unit d) five or more atoms per formula unit
b) three atoms per formula unit
Copper(I) sulfide a) two atoms per formula unit b) three atoms per formula unit c) four atoms per formula unit d) five or more atoms per formula unit
b) three atoms per formula unit
Iron(II) hydroxide a) two atoms per formula unit b) three atoms per formula unit c) four atoms per formula unit d) five or more atoms per formula unit
d) five or more atoms per formula unit
Aluminum phosphate a) two atoms per formula unit b) three atoms per formula unit c) four atoms per formula unit d) five or more atoms per formula unit
d) five or more atoms per formula unit
Chem 121 Chapter 5 Answers
energy
the ability to do work or transfer heat
thermodynamics
the study of energy an its transformations
thermochemistry
the study of chemical reactions and the energy changes that involve heat
Industrial Revolution
thermodynamics began during the __
release heat or absorb heat
chemical reactions can __
potential or kinetic
all forms of energy can be classified as __
potential energy
the energy that originates from chemical reactions is associated mainly with changes in __
electrostatic potential energy
the most important form of potential energy in molecules
joule
the unit of energy commonly used is the __
1 J = 1(kg m^2/s^2)
1 J = __
electrostatic attraction
__ is seen between oppositely charged ions
formed, broken
energy is released when chemical bonds are __; energy is consumed when chemical bonds are __
first law of thermodynamics
Energy can be converted from one form to another, but it is neither created nor destroyed
chemical energy
To heat your home, __ needs to be converted to heat
sunlight
__ is converted to chemical energy in green plants
system
The portion of the universe that we single out to study
surroundings
everything else but the system
reactants and products, the container and everything beyond it
when studying the energy change that accompanies a chemical reaction in a laboratory, the __ constitutes the system; __ are considered the surroundings
1. open 2. closed 3. isolated
types of systems
open system
a region of the universe being studied that can exchange heat AND mass with its surroundings
closed system
a region of the universe being studied that can ONLY exchange heat with its surroundings (NOT mass)
isolated system
a region of the universe that can NOT exchange heat or mass with its surroundings
internal energy (E or ∆E)
the sum of all kinetic and potential energies of all components of the system
change in internal energy
the final energy of the system minus the initial energy of the system
∆E = E(final) – E(initial)
change in internal energy
1. a number 2. a unit 3. a sign
thermodynamic quantities have 3 parts:
magnitude of change
a number and a unit give the __
direction
the sign gives the __
E(final) > E(initial)
a positive value of ∆E results when __
absorbed
a positive value of ∆E indicates the system has __ energy from its surroundings
E(final) < E(initial)
a negative value of ∆E results when __
released
a negative value of ∆E indicates the system has __ energy from its surroundings
gains
A positive ΔE results when the system __ energy from the surroundings
loses
A negative ΔE results when the system __ energy to the surroundings
direction of energy flow
signs only show __
decrease in the energy of the surroundings
any increase in the energy of the system is accompanied by a __
heat or work
a system may exchange energy with its surroundings through __
ΔE = q + w
ΔE with heat and work
q
heat
w
work
endothermic
When heat is absorbed by the system from the surroundings, the process is __
exothermic
When heat is released by the system into the surroundings, the process is __
extensive
energy is an __ property
total quantity of matter in a system
the internal energy of a system is proportional to the __
internal energy
Usually we have no way of knowing the __ of a system
independent
we do know that the internal energy of a system is __ of the path by which the system achieved that state.
state function
internal energy is a __
state functions
a property of a system that is determined by specifying the system’s condition or state
present state of the system
the value of a state function depends only on the __, not on the path by which the system arrived at that state
E(initial) and E(final)
ΔE depends only on __, not on how the change occurred
not state functions
q and w are __
enthalpy
at constant pressure, the change in __ is the heat gained or lost
1. Enthalpy is an extensive property. 2. The enthalpy change for a reaction is equal in magnitude, but opposite in sign, to ΔH for the reverse reaction. 3. The enthalpy change for a reaction depends on the states of the reactants and the products
3 truths about enthalpy
calorimetry
the measurement of heat flow
heat capacity
The amount of energy required to raise the temperature of a substance by 1 K (1 °C)
Chem 121 Chapter 6 Answers
Classify the following reactions as synthesis, decomposition, single-displacement, or double-displacement reactions. Drag the items to their respective bins. In a single-displacement reaction, one element displaces another in a compound. 2. In a double-displacement reaction, two elements or groups of elements in two different compounds exchange places to form two new compounds. 3. In a decomposition reaction, a complex substance breaks down into simpler substances. 4. In a synthesis reaction, simpler substances combine to form more complex substances.
Synthesis (combination) Ni+Cl2→NiCl2Ni+Cl2→NiCl2 C5H10+Br2→C5H10Br2 Decomposition 2H2O→2H2+O22H2O→2H2+O2 2NO→N2+O22NO→N2+O2 2Pb(NO3)2→2PbO+4NO2+O2 Single-displacement Zn+H2SO4→ZnSO4+H2 Double-displacement AgNO3+NaCl→ NaNO3+AgClAgNO3+NaCl→ NaNO3+AgCl CaCO3+2HCl→ CaCl2+H2CO3
An anion always a. contains a group of two or more atoms with a positive charge. b. contains a metal and a nonmetal. c. has a positive charge. d. has a negative charge. e. forms covalent bonds.
d. has a negative charge
What is the symbol for the ion with 19 protons and 18 electrons? a. K+ b. Ar+ c. F- d. K- e. F+
a. K+ (positively charged because the number of protons is greater than electrons.)
The number of electrons in an ion with 20 protons and an ionic charge of 2+ is
18 electrons (20-2=18.)
Elements in group 2A(2) of the periodic table form ions with a charge of
2+ reference periodic table
N3−N3−, used to build biomolecules
7,10 protons, electrons (An atom becomes an ion by gaining or losing electrons. The identity of an element depends on the number of protons in the nucleus (i.e., its atomic number), which is constant for all ions and isotopes. A proton has a charge of +1, and an electron has a charge of −1, and the charge of the ion depends on the difference between the number of protons and electrons.)
K+, the most prevalent positive ion in cells, needed for muscle contraction and nerve impulses
19,18 protons, electrons A neutral potassium atom has 19 protons and 19 electrons. Potassium loses an electron to become positively charged.
I−, needed for thyroid function
53,54 protons, electrons (A negative ion is referred to as an anion. Halides gain one electron to form a stable anion with a −−1 charge. The charges of anions should not be confused with the oxidation states of elements in molecules.)
Fe2+, needed for transport of oxygen from the lungs to cells
26,24 protons, electrons. (A positive ion is referred to as a cation. Alkali metals and alkaline-earth metals only form one type of cation by losing one and two electrons, respectively. Transition metals (in the dd block) can lose electrons from the ss or dd orbitals to form several types of cations (i.e., having different charges).)
Determine whether the following pairs of elements can form ionic compounds. 1. fluorine and sodium 2. iron and chlorine 3. lithium and fluorine 4. sulfur and calcium 5. sulfur and bromine 6. potassium and calcium
Do form ionic bonds: fluorine and sodium iron and chlorine lithium and fluorine sulfur and calcium Do not form ionic bonds: sulfur and bromine potassium and calcium (Any of the nonmetals in one of the ionic compounds could be exchanged for a nonmetal from another ionic compound. Nonmetals and metals can pair in almost any combination to make an ionic compound.)
What is the formula for an ionic compound that contains the elements magnesium and chlorine?
MgCl2 1 Mg with 2 Cl to fulfil the 8 valence electrons needed to create a bond.
The correct formula for a compound formed from the elements Al and O is
Al2O3 Fulfills 8 valence electrons in the bond.
Which one of the following compounds contains an ion with a 3+ charge?
FeCl3
The compound MgCl2 is named
magnesium chloride.
Which one of the following elements forms two or more ions with different ionic charges? 1. O 2. F 3. Ca 4. Fe 5. K
Fe
What is the formula for iron(III) oxide?
Fe2O3 (Two Fe3+ ions have a total charge of 2(+3)=+6 Three O2- ions have a total charge of 3(−2)=−6.)
What is the formula for strontium chloride?
SrCl2 (One Sr2+ ion has a charge of +2. Two Cl− ions have a total charge of 2(−1)=−2.)
Sort the following manganese compounds by whether the cation is manganese(II) or manganese(III).
Manganese(II) MnO MnBr2 Mn3P2 Manganese(III) MnN MnI3 Mn2S3 (Look at ionic charge to solve. make the charges equal 0)
1.Magnesium sulfate 2.Magnesium hydrogen sulfate 3.Magnesium sulfide 4. Magnesium sulfite 5. Magnesium hydrogen sulfite
1.MgSO4 2.Mg(HSO4)2 3.MgS 4.MgSO3 5.Mg(HSO3)2 (all subscripts “lowercase”)
A group of covalently bonded atoms that has an overall electrical charge is called a(n)
polyatomic ion
What is the formula of a compound that contains Na+ and PO43- ions?
Na3PO4 (all subscripts)
Fe2(SO4)3 is called
iron (III) sulfate
In a molecule with covalent bonding,
atoms are held together by sharing electrons
The types of compounds that use prefixes in their names are
covalent compounds.
N2O3
dinitrogen trioxide
To name molecular compounds using the chemical formulas and systematic naming rules. Binary molecular compounds are generally composed of two nonmetal atoms connected by covalent bonds. Nonmetal atoms are found in the upper right of the periodic table, although hydrogen is sometimes included in this group. In naming molecular compounds, Greek prefixes are used to indicate the number of atoms of each element present. If there is only one atom of the first element, the prefix mono is usually omitted. For example, CO2 is called carbon dioxide. Note that the ending of the second element is changed to ide.
NumberPrefix 1mono 2di 3tri 4tetra 5penta 6hexa 7hepta 8octa 9nona 10deca
Drag each item to the appropriate bin.
1 atom monochloride 2 atoms dibromide disulfide 3 atoms triiodide trisulfide 4 atoms tetrabromide tetrasulfide 5 atoms pentachloride 6 atoms hexabromide
The process of assigning names to compounds is dependent upon what type of compound is being named. Binary covalent compounds are named by stating the name of the first element (usually the less electronegative atom) followed by the name of the second element, changing the ending of the second compound to ide, and assigning Greek prefixes to denote how many atoms of each element are present in the compound. The Greek prefixes most commonly used are displayed in the table below:
PrefixMeaning mono1 di2 tri3 tetra4 penta5 hexa6 hepta7
The chemical formulas for various covalent compounds important to human physiology are shown below. Name them accordingly. 1. NO 2.N20 3.NO2 4.CO 5.CO2 6.PBr2
1.nitrogenmonoxide 2.dinitrogen monoxide 3.nitrogendioxide 4.carbon monoxide 5.carbondioxide 6.phosphorus tribromide
The ability of an atom to attract the shared electrons in a covalent bond is its
electronegativity.
Which of the following substances contains a nonpolar covalent bond?
N2
Which of the following elements has the lowest electronegativity?
Li
The VSEPR theory allows us to determine the most favorable
shape of a molecule.
The water molecule has a dipole with the negative portion
pointing toward the oxygen atom.
The shape of the ammonia molecule ( NH3 ) is
pyramidal
The shape of the carbon dioxide (CO2 ) is
linear
The shape of the water molecule ( H2O) is
bent
The ammonia molecule ( NH3 ) is
a polar molecule with polar bonds
The strongest interactions between molecules of ammonia ( NH3 ) are
hydrogen bonds.
The strongest interactions in the compound sodium fluoride, NaF, are examples of
ionic bonds.
The four major attractive forces between particles are ionic bonds, dipole-dipole attractions, hydrogen bonds, and dispersion forces. Consider the compounds below, and classify each by its predominant attractive or intermolecular force among atoms or molecules of the same type.
Ionic MgF2 H bonding H2O Dipole HBr Dispersion F2 (The strength of these attractive forces is directly proportional to the charge separation that occurs in the molecules. Ionic bonds involve oppositely charged ions, which have the greatest charge separation. Nonpolar molecules, which form momentary dipole moments, have dispersion forces and the smallest separation of charge. Ionic bonds are the strongest of these attractive forces, and dispersion forces are the weakest.) hottest-coldest
Identify each of the compounds as ionic or molecular. Drag the appropriate items to their respective bins.
Ionic iron(II) sulfate tin(II) fluoride Molecular carbon dioxide
A chemical equation is balanced when
the number of atoms of each element is the same in reactants and products.
In any balanced chemical equation, the number of each type of atom on both sides of the equation is
the same
Which of the following gives the balanced equation for this reaction? K3PO4 + Ca(NO3)2 → Ca3(PO4)2 + KNO3
2K3PO4 + 3Ca(NO3)2 → Ca3(PO4)2 + 6KNO3
In the following reaction, when the equation is correctly balanced, what is the correct coefficient for H2? Fe(s) + HCl(aq) → FeCl3(aq) + H2(g)
3
In a __________ reaction, two or more elements or compounds form one product.
combination
How many moles of iron are present in 3.15 × 1024 atoms of iron?
5.23 moles Submit
One mole of particles of any substance contains how many particles?
6.02 × 1023
How many molecules of water, H2O, are present in 75.0 g of H2O?
2.51 × 1024 molecules
The molar mass of potassium is
39.1 g
How many moles of water, H2O, are present in 75.0 g of H2O?
4.17 moles
Calculate the molar mass of potassium chloride, KCl.
74.6 g Submit
What is the molar mass of sodium phosphate, Na3PO4?
164.0
How many grams of glucose (C6H12O6) are in 3.55 moles of glucose?
639g
Given the following equation, what is the correct form of the conversion factor needed to convert the number of moles of O2 to the number of moles of Fe2O3 produced? 4Fe(s) + 3O2 (g) → 2Fe2O3(s)
2molesofFe2o3/3moles of O2
A)The number of moles of oxygen gas needed to react with 4.0 moles of Mg is B)The number of moles of MgO produced when 0.20 mole of O2 reacts completely is C)How many moles of magnesium are needed to react with 0.50 mole of O2?
A)2.0 moles B)0.40 moles C)1.0 moleS
How many moles of methane are produced when 59.6 moles of carbon dioxide gas react with excess hydrogen gas?
59.6 mol
How many moles of hydrogen gas would be needed to react with excess carbon dioxide to produce 53.6 of water vapor
107 mol
What type of reaction is: CH4 + 2O2 → CO2 + 2H2O + 218 kcal?
an exothermic reaction
Chem 121 Course Overview
A course in Chemistry at the sophomore or junior level for Biology, Chemistry and Engineering students that requires a laboratory component.
This course will cover topics such as: matter and measurement, atoms and elements, molecules and compounds, chemical reactions, gases, thermochemistry, the quantum-mechanical model of the atom; periodic properties of the elements; chemical bonding (the Lewis model & molecular shapes), valence bond theory. In addition to those topics we will also discuss liquids, solids and intermolecular forces..
Laboratory experiments relay many of the principles from lectures and give students hands-on experience with basic laboratory techniques and how to make observations rigorously.
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