Chem exam 4

1.      For the following reaction, which statement is not correct?

 

2Au + 4Cl₂ → 2AuCl₄^–

•      Au is the reducing agent

• Cl₂ is the oxidizing agent

• Au is oxidized

• Cl₂ is reduced.

• "The equation is balanced"

1.      You are given several processes below. Which one of the processes is spontaneous?

• a.      baking bread

• rusting of iron

• photosynthesis

•   studying for this exam

• frying an egg

1.      In the voltaic cell

Pb(s)  |  Pb²⁺(aq)  ||  Ag⁺(aq)  |  Ag(s)

• The anode is solid silver

• The cathode is the site of oxidation

• No salt bridge is necessary because the reaction is spontaneous

• One of the products is solid silver.

• None of the above

1.      The standard free energy, ΔG°, for the 2-electron oxidation of solid zinc by chlorine is −410 kJ/mole. What is the standard reduction potential of chlorine, if the standard reduction potential of zinc is −0.76 V?

• 1.36

• 1.23

• 1.42

• -1.23

• none of these

1.      What is the best description of what happens to Cu during this reaction?

Cu₂O(s)  +  2 H⁺(aq)  →  Cu(s)  +  Cu²⁺(aq)  +  H₂O(l)

• Copper undergoes a disproportionation reaction. 

• Copper undergoes an oxidation reaction

• Copper undergoes a reduction reaction

• Copper undergoes a decomposition reaction.

• Copper undergoes a synthesis reaction.

1.      Place the following in order of increasing (from lowest to highest) molar entropy at 298 K.

 

              NO            CO            SO

• NO  <  CO  <  SO

• SO  <  CO  <  NO

• SO  <  NO  <  CO

• CO  <  SO  <  NO

• CO  <  NO  <  SO

1.      A student attempts to learn the concentration of a dilute solution of Cu²⁺ by constructing a concentration cell with copper electrodes, the dilute solution and a 1M solution of the same ion. If the measured voltage of the cell is 0.030 V, and the standard reduction potential of Cu²⁺(aq) + 2e⁻  à  Cu(s) is 0.335 V, what is the concentration of the dilute solution? The temperature of the cell is 298 K.

• .34 M

• .034M

• .097M

• .21M

• .17M

1.      For a given reaction, ΔH = +7.50 kJ/mol and ΔS = +70.74 J/(K mol). Above what temperature is the reaction spontaneous?

•   −167 °C

• 298 °C

•   273 °C

• −112 °C

• 0 °C

1.      Which of the following is NOT a law of thermodynamics:

• Energy cannot be created or destroyed

• For a spontaneous process, the entropy of the universe increases.

• The entropy of a perfect crystal is zero at absolute zero.

• The force on an object is equal to its mass times its acceleration.

• None of the above

Select the true statement regarding this reaction.

MnO₄⁻(aq)  +  Pb²⁺(aq)  →  Mn²⁺(aq)  +  Pb⁴⁺(aq)

• MnO₄⁻ gets oxidized

• Pb²⁺ gets reduced

• MnO₄⁻ is the reducing agent

• Pb²⁺ is the reducing agent

• Pb²⁺ is the oxidizing agent