Question

Given : (i) $Cu(g)+2Ag^{+}(aq) \rightleftharpoons Cu^{2+}(aq)+2Ag(s)$, $K = \frac{[Cu^{2+}(aq)]}{[Ag^{+}(aq)]^{2}}$ = $2.0\times 10^{15}$ (ii) $Cu(s)+Zn^{2+}(aq) \rightleftharpoons Cu^{2+}(aq)+Zn(s)$, $K = \frac{[Cu^{2+}(aq)]}{[Zn^{2+}(aq)]}$ = $2.0 \times 10^{-19}$ Arrange the three metals in order of increasing reactivity.

Answer 1

$Cu(g) + 2Ag^+(aq) \rightarrow Cu^{2+} (aq) + 2Ag(s) ; K = 2.0\times 10^{15}$

$Cu(s) +Zn^{2+}(aq) \times Cu^{2+}(aq) + Zn(s) ; K =2.0\times 10^{-19}$

These are the two equations given whose reactivity we have to compare

K= $K_R/K_P$, where the numerator is for reactants and denominator is for products

Now for the first reaction the value of K (equilibrium constant) is very high i.e. of the range $2.0 x 10^{15}$ hence the numerator is greater that means the reactants will be more while for the second one the products will be more in number since K is of the range $2.0\times 10^{-19}$.

Answer 2

Answer:

Nernst Equation:-

E

cell

=E

cell

∘

−

nF

RT

lnQ----------1

E

cell

→Emf of cell.

E

cell

∘

→ Standard reduction potential.

R→ Universal gas constant.

T→ Temperature in Kelvin.

n→ moles of electrons.

F→ Faraday's constant.

Q→ Reaction Quotient.

2Ag

(aq)

+

+Cu

(s)

⇌Cu

(aq)

2+

+2Ag

(s)

----------2

Q=

[Reactants]

b

[Products]

a

a & b→ stoichiometric co-efficient of product & reactant respectively.

∴

(Ag

(aq)

+

)(Cu

(s)

)

(Cu

2+

)

aq

(Ag

s

)

2

=

[Ag

aq

+

]

2

[Cu

aq

2+

]

---------3 [

Cu

(s)

[Ag

s

]

2

=unity in pure form].

∴E

cell

=E

cell

∘

−

nF

RT

ln

[Ag

aq

+

]

2

[Cu

aq

2+

]

----------4

∴ From Equation 4, it is observed that E

(cell)

depends on the concentration of both Cu

2+

& Ag

+

. It increases with increase in concentration of Ag

+

.