MODEL PAPER 5 — Chemistry STD 12 Science — Question

$1.\,Zn|Z{n^{2 + }}\,\left( {1\,M} \right)||C{u^{2 + }}\left( {1\,M} \right)|Cu$

$2.\,Zn|Z{n^{2 + }}\,\left( {0.1\,M} \right)||C{u^{2 + }}\left( {1\,M} \right)|Cu$

$3.\,Zn|Z{n^{2 + }}\,\left( {1\,M} \right)||C{u^{2 + }}\left( {0.1\,M} \right)|Cu$

are represented by $E_1,\,E_2,\,E_3$. Which of the following statement is true?

$ \mathrm{Ag}^{+}+\mathrm{e}^{-} \rightarrow \mathrm{Ag} ; \mathrm{E}_{\text {red }}^{\circ}=0.8 \mathrm{~V} $

$ \mathrm{C}_6 \mathrm{H}_{12} \mathrm{O}_6+\mathrm{H}_2 \mathrm{O} \rightarrow \text { Gluconic acid }\left(\mathrm{C}_6 \mathrm{H}_{12} \mathrm{O}_7\right)+2 \mathrm{H}^{+}+2 \mathrm{e}^{-} ; \mathrm{E}_{\text {oxd }}^{\circ}=-0.05 \mathrm{~V} $

$ \mathrm{Ag}\left(\mathrm{NH}_3\right)_2^{+}+\mathrm{e}^{-} \rightarrow \mathrm{Ag}(\mathrm{s})+2 \mathrm{NH}_3 ; \mathrm{E}_{\text {red }}^{\circ}=0.337 \mathrm{~V}$

[Use $2.303 \times \frac{\mathrm{RT}}{\mathrm{F}}=0.0592$ and $\frac{\mathrm{F}}{\mathrm{RT}}=38.92$ at $298 \mathrm{~K}$ ]

$1.$ $2 \mathrm{Ag}^{+}+\mathrm{C}_6 \mathrm{H}_{12} \mathrm{O}_6+\mathrm{H}_2 \mathrm{O} \rightarrow 2 \mathrm{Ag}(\mathrm{s})+\mathrm{C}_6 \mathrm{H}_{12} \mathrm{O}_7+2 \mathrm{H}^{+}$

Find $\ln \mathrm{K}$ of this reaction.

$(A)$ $66.13$  $(B)$ $58.38$  $(C)$ $28.30$  $(D)$ $46.29$

$2.$ When ammonia is added to the solution, $\mathrm{pH}$ is raised to $11$ . Which half-cell reaction is affected by $\mathrm{pH}$ and by how much?

(A) $E_{\text {oxd }}$ will increase by a factor of $0.65$ from $E_{\text {oxd }}^{\circ}$

(B) $E_{\text {oxd }}$ will decrease by a factor of $0.65$ from $E_{\mathrm{cod}}^{\prime}$

(C) $\mathrm{E}_{\text {red }}$ will increase by a factor of $0.65$ from $\mathrm{E}_{\text {rod }}^{\circ}$

(D) $E_{\text {red }}$ will decrease by a factor of $0.65$ from $E_{\text {rod }}^2$

$3.$   Ammonia is always is added in this reaction. Which of the following must be incorrect?

$(A)$ $\mathrm{NH}_3$ combines with $\mathrm{Ag}^{+}$to form a complex.

$(B)$ $\mathrm{Ag}\left(\mathrm{NH}_3\right)_2^{+}$is a stronger oxidising reagent than $\mathrm{Ag}^{+}$.

$(C)$ In absence of $\mathrm{NH}_3$ silver salt of gluconic acid is formed.

$(D)$ $\mathrm{NH}_3$ has affected the standard reduction potential of glucose/gluconic acid electrode.

Give the answer question $1,2$ and $3.$

${A_{\left( s \right)}} + {B^ \oplus } \longrightarrow {A^ \oplus } + {B_{\left( s \right)}}\,;\,\Delta {H^o} =  - 551.5\,KJ$ Calculate standard electrode potential of cell (in $volt$). .......... $\mathrm{volt}$

$CoCl_3 \cdot 6NH_3, CoCl_3 \cdot 5NH_3,CoCl_3\cdot 4NH_3$ respectively is