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Chemistry Straighterline Questions and complete solutions
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Chemistry Straighterline Questions and complete solutions
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Chemistry Straighterline Q&AWhat element has been oxidized and what element has been reduced in the redox reaction shown?
3CuS + 8HNO3 ==> 3CuSO4 + 8NO + 4H20
Select one:
a. Copper has been oxidized; nitrogen has been reduced.
b. Nitrogen has been oxidized; oxygen has been reduced.
c. Sulfur has been oxidized; nitrogen has been reduced.
d. Oxygen has been oxidized; copper has been reduced.
c. Sulfur has been oxidized; nitrogen has been reduced.
When iron ions react with water, some of the iron ions will combine with water molecules, like this:
Fe3+(aq) + 3H2O(l) à Fe(OH)3(s) + 3H+(aq)
In this case, is the iron ion acting like an acid or a base? Explain.
A. The iron ion is acting like a base. It is forcing water to give up a hydronium ion, which agrees with
the Brønsted-Lowry definition of an acid.
B. The iron ion is acting like an acid. It has accepted a pair of electrons from the oxygen, which agrees
with the Lewis definition of an acid.
C. The iron is not acting like either an acid or a base. It is a reducing agent because it has been
oxidized.
D. The iron ion is acting like an acid. It is removing hydroxide from the solution, which agrees with the
Arrhenius definition of an acid.
B. The iron ion is acting like an acid. It has accepted a pair of electrons from the oxygen, which agrees
with the Lewis definition of an acid.
Ammonia is a vitally important industrial chemical. Fertilizers and nitric acid (an important industrial
chemical itself) are produced from ammonia. The Haber-Bosch process is used to create ammonia,
and has two major steps:
a) CH4(g) + H2O(g) à 2 H2(g) + CO(g)
b) 3 H2(g) + N2(g) à 2 NH3(g)
Is either of these steps an oxidation-reduction reaction? If so, identify which elements are oxidized,
which are reduced and which are neither oxidized nor reduced.
A. Both of these steps are oxidation-reduction reactions.
B. Only reaction b) is an oxidation-reduction reaction.
C. Only reaction a) is an oxidation-reduction reaction.
D. No, neither of these reactions is an oxidation-reduction reaction.
A. Both of these steps are oxidation-reduction reactions.
,Calculate Ecell for the galvanic cell based on these half-reactions at 25oC, in which [H2SO4] = 0.5 M
HSO4- (aq) + Pb (s) H+ (aq) + PbSO4 (s) + 2 e- Eo = +0.35 V
PbO2 (s) + 3H+ (aq) + HSO4- (aq) + 2 e- PbSO4 (s) + 2H2O (l) Eo = +1.46 V
If the concentration of sufuric acid is increased, will Ecell increase or decrease? Explain.
A. This question cannot be answered with the information given. Concentrations of the other
reactants and products are necessary.
B. Ecell = 1.80 V. Changing the concentration of sulfuric acid will increase Ecell because log Q will
become smaller.
C. Ecell = 1.81 V. Changing the concentration of sulfuric acid will not change Ecell.
D. Ecell = 1.79 V. Changing the concentration of sulfuric acid will increase Ecell because log Q will
become smaller.
D. Ecell = 1.79 V. Changing the concentration of sulfuric acid will increase Ecell because log Q will
become smaller.
Acetic acid is a very important industrial chemical and is produced by this reaction:
CH3OH(l) + CO(g) à CH3COOH(l)
Calculate the value of the standard Gibbs Free Energy change for this reaction. Is acetic acid
thermodynamically stable compared with liquid water at standard conditions? Explain.
Compound
Standard Gibbs Free Energy (kJ/mol)
H2O (l)
-237.1
CH3COOH
-389.9
CH3OH (I)
-166.6
CO (g)
-137.3
A. ΔG°rxn = -86.0 kJ; At standard conditions, acetic acid is less thermodynamically stable than water
because it has a more negative value of ΔG°.
B. ΔG°rxn = -86.0 kJ; At standard conditions, acetic acid is more thermodynamically stable than water
because it has a more negative value of ΔG°.
C. ΔG°rxn = +86.0 kJ; At standard conditions, acetic acid is less thermodynamically stable than water
because it has a more negative value of ΔG°.
,D. . ΔG°rxn = -0.017 kJ; At standard conditions, acetic acid is less thermodynamically stable than water
because it has a more negative value of ΔG°.
A. ΔG°rxn = -86.0 kJ; At standard conditions, acetic acid is less thermodynamically stable than water
because it has a more negative value of ΔG°.
Acetylene (properly known as ethyne) and calcium hydroxide are the products of the reaction
between calcium carbide (CaC2) and water. Ethyne can be easily set on fire. This can be done on the
surface of an ice cube, giving it the appearance of "burning ice". Identify the balanced reaction for the
combustion of ethyne and explain why it burns with intense heat.
A. 2C2H2 + 5O2 à 4CO2 + 2H2O; There is a lot of energy released in this reaction because there is a
triple bond between the carbons in ethyne, which contains a lot of energy, and this energy is released
when the bonds are broken.
B. C2H4 + 3O2 à 2CO2 + 2H2O; There is a lot of energy released in this reaction because there is a
double bond between the carbons in ethyne, which contains a lot of energy, and this energy is
released when the bonds are broken.
C. C2H4 + 3O2 à 2CO2 + 2H2O; There is a lot of energy released in this reaction because the energy
released when forming the chemical bonds in two moles of CO2 and two moles of water H2O is much
more than the energy required to break the chemical bonds in one mole of ethyne and three moles of
oxygen.
D. 2C2H2 + 5O2 à 4CO2 + 2H2O; There is a lot of energy released in this reaction because the energy
released when forming the chemical bonds in four moles of CO2 and two moles of water H2O is much
more than the energy required to break the chemical bonds in two moles of ethyne and five moles of
oxygen.
D. 2C2H2 + 5O2 à 4CO2 + 2H2O; There is a lot of energy released in this reaction because the energy
released when forming the chemical bonds in four moles of CO2 and two moles of water H2O is much
more than the energy required to break the chemical bonds in two moles of ethyne and five moles of
oxygen.
In some enzymatic reactions, the product of the reaction that is catalyzed by the enzyme is able to
bind to the active site on the enzyme itself. What effect would this have on the activity of the
enzyme? Could this be a biologically useful feature in some situations? Explain.
A. This would inhibit the enzyme's activity, slowing it down. No, this could not be biologically useful
and is the sign of a damaged enzyme. Enzymes should catalyze as many reactions as possible for
biological efficiency.
B. This would enhance the enzyme's activity, speeding it up. Yes, this could be biologically useful
because it would maximize production of the product.
C. This would inhibit the enzyme's activity, slowing it down. Yes, this could be biologically useful
because it could prevent over-production of the product.
D. This would enhance the enzyme's activity, slowing it down. No, this would not be biologically useful
because it would cause the enzyme to be less efficient.
C. This would inhibit the enzyme's activity, slowing it down. Yes, this could be biologically useful
because it could prevent over-production of the product.
Silicon can be "doped" with other elements by adding small amounts of those elements to the silicon.
This can make "n-type" or "p-type" semiconductors, depending on what is added to the silicon. What
, type of semiconductor would be produced by adding indium to silicon? Why? Which element could
you add to make the opposite type of semiconductor?
A. Doping silicon with indium produces a "p-type" semiconductor. This is because the indium has
more protons than silicon, so it is a "p-type" semiconductor. Adding arsenic to silicon would produce
an "n-type" semiconductor.
B. Doping silicon with indium produces a "n-type" semiconductor. This is because the indium has
more neutrons than silicon, so it is an "n-type" semiconductor. Adding arsenic to silicon would
produce a "p-type" semiconductor.
C. There is not enough information to answer this question. To know what type of semiconductor will
be produced requires knowledge of the band-gap energies of each of the elements involved.
D. Doping silicon with indium produces a "p-type" semiconductor. This is because the indium has
fewer valence electrons than silicon, and this will produce positively charged "holes" in the electron
structure. Adding arsenic to silicon would produce an "n-type" semiconductor.
D. Doping silicon with indium produces a "p-type" semiconductor. This is because the indium has
fewer valence electrons than silicon, and this will produce positively charged "holes" in the electron
structure. Adding arsenic to silicon would produce an "n-type" semiconductor.
Atoms that have the same number of protons but different numbers of neutrons are called
Isotopes
We have an expert-written solution to this problem!
proposed an atomic theory in 1808.
John Dalton
The magnitude of the electron charge was discovered by
R. Millikan
E. Rutherford is credited with discovering the
Nucleus
Metals and non-metals are separated in the periodic table by a(n)
Staircase
Horizontal rows in the periodic table are called
Periods
In a chemical reaction, the reactant that is used up first is the ___________.
Limiting reagent
The concentration of a solution is termed its ________.
Molarity
The chemical formula of a compound determined from its molecular mass is called the
____________.
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