Friday
July 31, 2015

Homework Help: Chem Check Please!!!

Posted by Chris on Friday, May 2, 2014 at 11:10pm.

1) Assuming the following reaction proceeds in the forward direction,
3 Sn4+(aq) + 2 Cr(s) ---> 3 Sn2+(aq) + 2 Cr3+(aq)
a.Sn4+(aq) is the reducing agent and Cr(s) is the oxidizing agent.

b.Cr(s) is the reducing agent and Sn2+(aq) is the oxidizing agent.

c.Sn4+(aq) is the reducing agent and Sn2+(aq) is the oxidizing agent.

d.Cr(s) is the reducing agent and Cr3+(aq) is the oxidizing agent.

e.Cr(s) is the reducing agent and Sn4+(aq) is the oxidizing agent.

The answer C




2) Write a balanced chemical equation for the oxidation of Cd(s) by concentrated nitric acid, producing NO2(g) and Cd2+(aq).
a. HNO3(aq) + Cd(s) ---> Cd2+(aq) + NO2(g) + OH(aq)
b. 2 HNO3(aq) + Cd(s) ---> Cd2+(aq) + 2 NO2(g) + 2 OH(aq)
c. HNO3(aq) + Cd(s) + H+(aq) ---> Cd2+(aq) + NO2(g) + H2O()
d. 4 HNO3(aq) + Cd(s) ---> Cd2+(aq) + 2 NO2(g) + 2H2O() + 2 NO3(aq)
e. HNO3(aq) + Cd(s) ---> Cd2+(aq) + NO2(g)


the answer is D



3) Consider the following half-reactions:
Cl2(g) + 2 e -> 2 Cl(aq) E = +1.36 V
Ag+(aq) + e -> Ag(s) E = +0.80 V
Cu2+(aq) + 2 e -> Cu(s) E = +0.34 V
Sn2+(aq) + 2 e -> Sn(s) E = 0.14 V
Al3+(aq) + 3 e -> Al(s) E = 1.66 V
Which of the above elements or ions will reduce Cu2+(aq)?
a. Ag(s) and Sn2+(aq)
b. Cl(aq) and Ag(s)
c. Cl2(g) and Ag+(aq)
d. Sn(s) and Al(s)
e. Sn2+(aq) and Al3+(aq)

the answer is D


4)Given the following two half-reactions, write the overall balanced reaction in the direction in which it is spontaneous and calculate the standard cell potential.
Ga3+(aq) + 3 e -> Ga(s) E = 0.53 V
Sn4+(aq) + 2 e -> Sn2+(aq) E = +0.15 V
a. 2 Ga3+(aq) + 3 Sn2+(aq) -> 2 Ga(s) + 3 Sn4+(aq) = +0.68 V
b. 3 Ga3+(aq) + 2 Sn2+(aq) ->3 Ga(s) + 2 Sn4+(aq) = 1.89 V
c. 2 Ga(s) + 3 Sn4+(aq) -> 2 Ga3+(aq) + 3 Sn2+(aq) = +0.68 V
d. 3 Ga(s) + 2 Sn4+(aq) -> 3 Ga3+(aq) + 2 Sn2+(aq) = +0.38 V
e. 2 Ga(s) + 3 Sn4+(aq) -> 2 Ga3+(aq) + 3 Sn2+(aq) = +1.89 V

the answer is D

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