Straighterline Chemistry Final- deck 5

Straighterline Chemistry Final- deck 5 What element has been oxidized and what element has been reduced in the redox reaction shown?3CuS + 8HNO3 ==> 3CuSO4 + 8NO + 4H20

Select one:

• Copper has been oxidized; nitrogen has been reduced.
• Nitrogen has been oxidized; oxygen has been reduced.
• Sulfur has been oxidized; nitrogen has been reduced.
• Oxygen has been oxidized; copper has been reduced. - Correct Answer 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.

• 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.

• 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.

• The iron is not acting like either an acid or a base. It is a reducing agent because it

has been oxidized.

• The iron ion is acting like an acid. It is removing hydroxide from the solution, which

agrees with the Arrhenius definition of an acid. - Correct Answer 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)

• 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.

• Both of these steps are oxidation-reduction reactions. 1 / 2

• Only reaction b) is an oxidation-reduction reaction.
• Only reaction a) is an oxidation-reduction reaction.
• No, neither of these reactions is an oxidation-reduction reaction. - Correct Answer 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.

• This question cannot be answered with the information given. Concentrations of the

other reactants and products are necessary.

• Ecell = 1.80 V. Changing the concentration of sulfuric acid will increase Ecell

because log Q will become smaller.

• Ecell = 1.81 V. Changing the concentration of sulfuric acid will not change Ecell.
• Ecell = 1.79 V. Changing the concentration of sulfuric acid will increase Ecell

because log Q will become smaller. - Correct Answer 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

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