Question

4. By assigning oxidation numbers, identify the oxidising agent and the reducing agent
in each of the following reactions.
(a) 2Mg(s) + O2(g) → 2MgO(s)
(b) 2Na(s) + Br2(g) → 2NaBr(s)
(c) Br2 + 2KI → 2KBr + I2
(d) Fe2O3 + C → Fe + CO2
(e) 2NH3 + 3CuO → 3Cu + 3H2O + N2


5. The cell potential, or electromotive force (emf) is important because it is related to
the maximum electrical work that can be obtained from an electrochemical cell. A
voltaic cell is constructed that uses the following reaction and operates at 298K:
Zn(s) + Ni2+(aq) -> Zn2+(aq) + Ni(s)

Given that:
Half reaction Standard Reduction Potential (Ered)
Ni2+(aq) + 2e- --> Ni(s) -0.280 V
Zn2+(aq) + 2e- --> Zn(s) -0.763 V
(a) What is the emf of this cell under standard conditions?

Answer 1

Answer on question #57953 - Chemistry - Inorganic Chemistry

Question:

4. By assigning oxidation numbers, identify the oxidising agent and the reducing agent in each of the following reactions.

(a) $2 \mathrm{Mg}(\mathrm{s}) + \mathrm{O} 2(\mathrm{g}) \rightarrow 2 \mathrm{MgO}(\mathrm{s})$

(b) $2 \mathrm{Na}(\mathrm{s}) + \mathrm{Br} 2(\mathrm{g}) \rightarrow 2 \mathrm{NaBr}(\mathrm{s})$

(c) $\mathrm{Br}2 + 2\mathrm{KI} \rightarrow 2\mathrm{KBr} + \mathrm{I}2$

(d) $\mathrm{Fe}2\mathrm{O}3 + \mathrm{C} \rightarrow \mathrm{Fe} + \mathrm{CO}2$

(e) $2 \mathrm{NH} 3 + 3 \mathrm{CuO} \rightarrow 3 \mathrm{Cu} + 3 \mathrm{H} 2 \mathrm{O} + \mathrm{N} 2$

5. The cell potential, or electromotive force (emf) is important because it is related to the maximum electrical work that can be obtained from an electrochemical cell. A voltaic cell is constructed that uses the following reaction and operates at 298K:

$$\mathrm{Zn(s)} + \mathrm{Ni}^{2+} (\mathrm{aq}) \rightarrow \mathrm{Zn}^{2+} (\mathrm{aq}) + \mathrm{Ni(s)}$$

Given that:

Half reaction Standard Reduction Potential (Ered)

$\mathrm{Ni}^{2+} (\mathrm{aq}) + 2\mathrm{e}^{-} \rightarrow \mathrm{Ni(s)} -0.280 \mathrm{~V}$

$\mathrm{Zn}^{2+} (\mathrm{aq}) + 2\mathrm{e}^{-} \rightarrow \mathrm{Zn(s)} -0.763 \mathrm{~V}$

(a) What is the emf of this cell under standard conditions?

Solution:

4. (a) $2Mg_{(s)}^{0} + O_{2(g)}^{0} \rightarrow 2Mg^{+2}O_{(s)}^{-2}$; Mg - reducing agent, O₂ - oxidising agent.

(b) $2Na_{(s)}^{0} + Br_{2(g)}^{0} \rightarrow 2Na^{+1}Br_{(s)}^{-1}$; Na - reducing agent, Br₂ - oxidising agent.

(c) $Br_{2}^{0} + 2K^{+1}I^{-1} \rightarrow 2K^{+1}Br^{-1} + I_{2}$; KI - reducing agent, Br₂ - oxidising agent.

(d) $2Fe_{2}^{+3}O_{3}^{-2} + 3C^{0} \rightarrow 4Fe^{0} + 3C^{+4}O_{2}^{-2}$; C - reducing agent, Fe₂O₃ - oxidising agent.

(e) $2N^{-3}H_{3}^{+1} + 3Cu^{+2}O^{-2} \rightarrow 3Cu^{0} + 3H_{2}^{+1}O^{-2} + N_{2}^{0}$; NH₃ - reducing agent, CuO - oxidising agent.

5. (a) $\mathrm{emf} = \mathrm{Ered}\left(\frac{Ni^{2+}}{Ni^{0}}\right) - \mathrm{Ered}\left(\frac{Zn^{2+}}{Zn^{0}}\right) = -0.280 \mathrm{~V} - (-0.763 \mathrm{~V}) = 0.483 \mathrm{~V}$

Answer:

4. (a) Mg - reducing agent, O₂ - oxidising agent.

(b) Na - reducing agent, Br₂ - oxidising agent.

(c) KI - reducing agent, Br₂ - oxidising agent.

(d) C - reducing agent, Fe₂O₃ - oxidising agent.

(e) NH₃ - reducing agent, CuO - oxidising agent.

5. (a) $\mathrm{emf} = 0.483 \mathrm{~V}$

http://www.AssignmentExpert.com/