MID-TERM EXAMINATION

If something is reduced, it is formally losing electrons.

• TRUE

• FALSE

A reducing agent gets oxidized as it reacts.

• TRUE

• FALSE

Oxidizing agents can convert CO to CO₂.

• TRUE

• FALSE

Which of the following balanced equation that involve oxidation-reduction? (choose 2 answers)

• PBr_3(aq) + 3H₂O_(l) --> H₃PO_3(aq) + 3HBr_(aq)

• 3SO_2(g) + 2HNO_3(aq) + 2H₂O_(l) --> 3H₂SO_4(aq) + 2NO_(g)

• NaI_(aq) + 3HOCl_(aq) --> NaIO_3(aq) + 3HCl_(aq)

• 2H₂SO_4(aq) + 2 NaBr_(s) --> Br_2((l) + SO_2(l) + Na₂SO_4(aq) +2

Hydrazine (N₂H₄) and dinitrogen tetroxide form a self-igniting mixture that has been used as a rocket propellant. The reaction products are N₂ and H₂O. Write the balanced chemical reaction and identify the reducing agent (RA) and oxidizing agent (OA), respectively.(2 points)

Identify whether the half-reaction is an oxidation or reduction: H₂SO_3(aq) --> SO_4(aq)^-2 (acidic solution)

Write the balanced half-cell reaction of the (anode and cathode, respectively) chemical reaction:

NO_2(aq)^- + Al_(s) --> NH_4(aq)⁺ +AlO_2(aq)^- (basic solution) (2 points)

• anode: Al + 4OH^- --> AlO₂^- + 2H₂O +6e^-

  cathode: NO^-₂ + 6H₂O +3e^- --> NH₄⁺ + 8OH^-

• anode: Al + 4OH^- --> AlO₂^- + 2H₂O +6e^-

  cathode: NO^-₂ + 6H₂O +6e^- --> NH₄⁺ + 8OH^-

• anode: Al + 4OH^- --> AlO₂^- + 2H₂O +3e^-

  cathode: NO^-₂ + 6H₂O +3e^- --> NH₄⁺ + 8OH^-

• anode: Al + 4OH^- --> AlO₂^- + 2H₂O +3e^-

  cathode: NO^-₂ + 6H₂O +6e^- --> NH₄⁺ + 8OH^-

In the balanced oxidation-reduction equation, identify the elements that undergo changes in oxidation number and indicate the magnitude of the change:

2Hg⁺² + N₂H₄ --> 2Hg + N₂ + 4H⁺

• Hg: 0 to +2; N: -2 to 0

• Hg: +2 to 0; N: 0 to -2

• Hg: +2 to 0; N: -2 to 0

• Hg: 0 to +2; N: 0 to -2

A voltaic cell is constructed that uses the following reaction and operates at 298K

Zn_(s) + Ni⁺² --> Zn⁺² + Ni

What is the emf of the cell under standard conditions?(3-points)

• E⁰ = 1.01 V

• E⁰ = -1.01 V

• E⁰ = -0.51V

• E⁰ = 0.51V

The statement below refers to a comparison between two radioisotopes, A and X. Indicate whether the statement is TRUE or FALSE, and WHY.

If X is "not radioactive", its half-life is essentially zero. (2 points)