EMF

Trending Questions

Q. Calculate the solubility of

A_{2} X_{3}

in pure water, assuming that neither kind of ion reacts with water. The solubility product of

A_{2} X_{3}, K_{s p} = 1.1 \times 10^{- 23} .

$2.5 \times 10^{- 5} m o l L^{- 1}$
$1.5 \times 10^{- 5} m o l L^{- 1}$
$1.0 \times 10^{- 5} m o l L^{- 1}$
$2.0 \times 10^{- 5} m o l L^{- 1}$

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Q. Electromotive force (EMF) of a cell is

The potential required to oxidize one mole of ions.
The potential difference between electrode and electrolyte in a cell.
The difference between the reduction potential of cathode and anode.
None of the above.

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Q. For the electrochemical cell,

M | M^{+} | | X | X^{-}

E_{M^{+} / M}^{0} = 0.44 V

and

E_{X / X^{-}}^{0} = 0.33 V

From these data one can deduce that:

$M + X \to M^{+} + X^{-}$ is a spontaneous reaction
$M^{+} + X^{-} \to M + X$ is a spontaneous reaction
$E_{cell}^{0} = 0.77 V$
$E_{cell}^{0} = - 0.77 V$

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For a spontaneous reaction $△$ G, equilibrium constant (K) and $E_{c e l l}^{\circ}$ will be respectively:

-ve, > 1, +ve
+ve, > 1, -ve
-ve, < 1, -ve
-ve, > 1, -ve

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Q. Consider the following half cells

C u_{(s)} \to C u_{(a q)}^{2 +} + 2 e^{-}; E^{o} = - 0.325 V

C u_{(a q)}^{+} + e^{-} \to C u_{(s)}; E^{o} = 0.50 V

The

E^{o}

for the reaction

2 C u_{(a q)}^{+} \to C u_{(a q)}^{2 +} + C u_{(s)}

0.175 V
0.35 V
0.675 V
0.3375 V

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Q. Given that the standard potential (

E^{\circ}

) of

C u^{2 +} / C u

and

C u^{+} / C u

are

0.340 V

and

0.522 V

respectively. The

E^{\circ}

C u^{2 +} / C u^{+}

is:

$- 0.182 V$
$- 0.158 V$
$+ 0.158 V$
$0.182 V$

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Z n | Z n S O_{4} (0.01 M) | | C u S O_{4} (1.0 M) | C u

The emf of the cell is

E_{1}

. When the concentration of

Z n S O_{4}

is changed to

1.0 M

and that of

C u S O_{4}

changed to

0.01 M

, the emf changes to

E_{2}

. From the following, which one is the relationship between

E_{1}

and

E_{2}

?
(Given,

\frac{R T}{F} = 0.059)

$E_{1} = E_{2}$
$E_{1} < E_{2}$
$E_{1} > E_{2}$
$E_{2} = 0 \neq E_{1}$

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Q. Find EMF of cell

N i | N i^{2 +} | | A u^{3 +} | A u

N i^{2 +} | N i; E^{\circ} = - 0.25 V

A u^{3 +} | A u; E^{\circ} = 1.5 V

1.25 V
-1.25 V
1.75 V
0.83 V

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Q. The emf of the cell with the cell reaction given below is

0.28 V

25^{o} C

Z n (s) + 2 H^{+} (a q) \to Z n^{2 +} (a q, 0.1 M) + H_{2} (g, 1 a t m)

Calculate the

p H

of the hydrogen electrode
Given:

E_{Z n^{2 +} / Z n}^{0} = - 0.76 V

E_{H^{+} / H_{2}}^{0} = 0 V

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Q. When an ammeter connected between the anode and cathode idicates a zero reading, then the emf of the cell is zero.

True
False

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Q. In the replacement reaction,

The reaction will be most favourable if

M

happens to be:

$L i$
$R b$
$N a$
$K$

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Q. Given below are the half - cell reactions

M n^{2 +} + 2 e^{-} \to M n; E^{\circ} = - 1.18 e V

2 (M n^{3 +} + e^{-} \to M n^{2 +}); E^{0} = + 1.51 e V

The

E^{\circ}

for

3 M n^{2 +} \to M n + 2 M n^{3 +}

will be

-2.69 V; the reaction will not occur
-2.69 V; the reaction will occur
-0.33 V; the reaction will not occur
-0.33 V; the reaction will occur

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Q. Calculate the pressure of hydrogen passed through cathode half cell at

298 K

P t (s) | H_{2} (g, 800 t o r r) | H C l (a q) | H_{2} (g, p_{2}) | P t (s)

Given:

E_{c e l l} = 0.018 V 10^{2.3} \approx 200

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Q. Calculate the concentration of electrolyte (

C_{1}

) at anode for the given cell:

A g (s) | A g N O_{3} (a q, C_{1} M) | | A g N O_{3} (a q, C_{2} = 0.2 M) | A g (s)

The emf of the cell is

0.8 V

Take

A n t i l o g (13.5) = 3.16 \times 10^{13}

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