A voltaic cell consists of a Mn/Mn 2+ electrode ( E ° = –1.18 V) and a Fe/Fe 2+

Question

A voltaic cell consists of a Mn/Mn2+ electrode (E° = –1.18 V) and a Fe/Fe2+ electrode (E° = –0.44 V). Calculate [Fe2+] if [Mn2+] = 0.050 M and Ecell = 0.78 V at 25°C.

None of these choices is correct.

0.24 M

1.1 M

1.8 M

0.040 M

20 g O2

16 g O2

8 g O2

32 g O2

64 g O2

True

False

Complete and balance the following redox equation. Now sum the coefficients of all species in the balanced equation. (Remember to add the coefficients that are equal to one, and to add the coefficients of any species added to the equation.) The sum of the smallest whole number coefficients is

16

4

25

32

13

Cu(s) Cu2+(aq) + 2e–

Cu(s) + 2Ag+(aq) Cu2+(aq) + 2Ag(s)

Ag+(aq) + e– Ag(s)

Ag(s) Ag+(aq) + e–

Cu2+(aq) + 2e– Cu(s)

5.8 × 104 C

1.9 × 104 C

0.60 C

3.0 C

9.7 × 104 C

Cl–(aq)

RuO4(s)

[PtCl4]2–(aq)

H4XeO6(aq)

HFeO4–(aq)

–3.94 × 105 kJ/mol.

–7.87 × 102 kJ/mol.

–3.94 × 102 kJ/mol.

–1.97 × 105 kJ/mol.

–7.87 × 105 kJ/mol.

5.18 × 102 kJ/mol

1.79 kJ/mol

–1.04 × 103 kJ/mol

–1.79 kJ/mol

–3.45 × 102 kJ/mol

The cathode is always positive.

The anode is always negative.

The cathode is the electrode where the oxidation takes place.

Both oxidation and reduction make take place at the cathode, depending on the cell.

The cathode is the electrode where the reduction takes place.

A voltaic cell consists of a Mn/Mn2+ electrode (E° = –1.18 V) and a Fe/Fe2+ electrode (E° = –0.44 V). Calculate [Fe2+] if [Mn2+] = 0.050 M and Ecell = 0.78 V at 25°C.

Explanation / Answer

Q)

A voltaic cell consists of a Mn/Mn2+ electrode (E° = –1.18 V) and a Fe/Fe2+ electrode (E° = –0.44 V). Calculate [Fe2+] if [Mn2+] = 0.050 M and Ecell = 0.78 V at 25°C.

None of these choices is correct.

0.24 M

1.1 M

1.8 M

0.040 M

Answer:

the net E0= -0.44+1.18 V
                =0.74 V
the net reaction is Fe + Mn 2+= Fe 2++ Mn
[Mn2+] = 0.050 M and E°cell = 0.78 V at 25° C.
so, 0.78 = 0.74 +(0.059/2)(log s/0.05)
s0 log (s/0.05) = 1.355

so s = 1.134 M

Hence the correct option is 1.1 M

A voltaic cell consists of a Mn/Mn2+ electrode (E° = –1.18 V) and a Fe/Fe2+ electrode (E° = –0.44 V). Calculate [Fe2+] if [Mn2+] = 0.050 M and Ecell = 0.78 V at 25°C.

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