T-5 Electrochemistry

Question 1

When E > 0 the reaction is …

spontaneous forward or spontaneous in reverse?

Answer 1

forward

Question 2

When E < 0 the reaction is …

spontaneous forward or spontaneous in reverse?

Answer 2

reverse

Question 3

When E > 0 the delta G of the reaction is…

negative or positive?

Answer 3

negative

Question 4

When E < 0 the delta G of the reaction is…

negative or positive?

Answer 4

positive

Question 5

When E > 0 the reaction is …

electrolytic or voltaic?

Answer 5

voltaic

Question 6

When E < 0 the reaction is …

electrolytic or voltaic?

Answer 6

electrolytic

Question 7

Is the following an oxidation or reduction 1/2 reaction?

Cu²⁺ + 2e^- → Cu

Answer 7

reduction

Question 8

Is the following an oxidation or reduction 1/2 reaction?

Al → Al³⁺ + 3e^-

Answer 8

oxidation

Question 9

How many electrons are transfered in the following redox reaction?

Fe + 3 Ag⁺ ⇒ Fe³⁺ + 3 Ag

Answer 9

3 electrons are transfered from the Iron atom to the 3 silver ions

Question 10

How many electrons are transfered in the following redox reaction?

2 H₂O₂ (aq) ⇒ 2 H₂O (g) + O₂ (g)

Answer 10

2 electrons are transfered. One peroxide oxygen transfers an electron to the other so you get 0 and -2 oxidation numbers. There are two peroxide molecules present so a total of 2 electrons are transfered. This is a tough one.

Question 11

Which species is most likely to be reduced?

K⁺ + e^- → K E° = -2.93 V

Na⁺ + e- → Na E° = -2.71 V

Answer 11

sodium ion

Question 12

Which species is most likely to be oxidized?

Na⁺ + e^- → Na E° = -2.71 V

Br₂ + e^- → 2 Br^- E° = 1.07 V

Answer 12

Na⁺

Question 13

What are the half reactions for the following reaction?

2 Fe + 3I₂ → 2 Fe^₃₊ + 6I^-

Answer 13

Fe → Fe³⁺ + 3e_^-

I₂ + 2e^- → 2I^-

Question 14

What are the half reactions for the following reaction?

2Au³⁺ + 3Pt → 2Au + 3Pt²⁺

Answer 14

Au³⁺ + 3e- → Au

Pt → Pt²⁺ + 2e^-

Question 15

How many electrons are transfered in the following redox reaction?

2 Na (s) + 2 H₂O (l) ⇒ 2 NaOH (aq) + H₂ (g)

Answer 15

2 electrons are transfered from the sodium atoms to two of the hydrogen atoms in the water molecules.

Question 16

What reaction happens at the anode in a galvanic cell based on the following half cells?

Na⁺ + e^- → Na E° = -2.71 V

Br₂ + e^- → 2 Br^- E° = 1.07 V

Answer 16

Na → Na⁺ + e^- E° = 2.71 V

Question 17

What reaction happens at the cathode in a galvanic cell based on the following half cells?

K⁺ + e^- → K E° = -2.93 V

Na⁺ + e^- → Na E° = -2.71 V

Answer 17

Na⁺ + e^- → Na E° = -2.71 V

Question 18

What reaction happens at the cathode in a galvanic cell based on the following half cells?

Au³⁺ + 3e^- → Au

Pt → Pt²⁺ + 2e^-

Answer 18

Au³⁺ + 3e^- → Au

Question 19

What reaction happens at the anode in a galvanic cell based on the following half cells?

Fe → Fe³⁺ + 3e^-

I₂ + 2e^- → 2I^-

Answer 19

Fe → Fe³⁺ + 3e^-