A volume of x mL of 5 M solution was mixed with 10 mL of 2 M solution to make an electrolytic buffer. If the same buffer was used in the following electrochemical cell to record a cell potential of 235.3 mV, then the value of x = __________ m

Question

A volume of x mL of 5 M ${NaHCO}_{3}$ solution was mixed with 10 mL of 2 M $H_{2} {CO}_{3}$ solution to make an electrolytic buffer. If the same buffer was used in the following electrochemical cell to record a cell potential of 235.3 mV, then the value of x = __________ mL (nearest integer).

$Sn (s) | Sn {(OH)}_{6}^{2 -} (0.5 M) | {HSnO}_{2}^{-} (0.05 M) | {OH}^{-} | {Bi}_{2} O_{3} (s) | Bi (s)$

Consider upto one place of decimal for intermediate calculations [2026]

Given:

$[\begin{matrix} E_{{HSnO}_{2}^{-} | S n {(OH)}_{6}^{2 -}}^{\circ} = - 0.9 V \\ E_{{Bi}_{2} O_{3} | Bi}^{\circ} = - 0.44 V \\ p K a_{(H_{2} {CO}_{3})} = 6.11 \\ \frac{2.303 R T}{F} = 0.059 V \\ Antilog (1.29) = 19.5 \end{matrix}]$

Smart Achievers · Accepted Answer

(78)

We have considered

$E_{{[S n {(O H)}_{6}]}^{2 -} / H S n O_{2}^{-}}^{\circ} = - 0.9 V$

$Pt | {HSnO}_{2}^{-} (aq), {[Sn {(OH)}_{6}]}^{2 -} (aq), {OH}^{-} (aq) | {Bi}_{2} O_{3} (s) | Bi (s) |$

$0.5 M 0.05 M$

$E_{cell}^{\circ} = + 0.9 - 0.44 = 0.46 V$

$Oxidation Half:$

${HSnO}_{2}^{-} + H_{2} O + 3 {OH}^{-} \to {[Sn {(OH)}_{6}]}^{2 -} + 2 e^{-}$

$Reduction half:$

${Bi}_{2} O_{3} + 3 H_{2} O + 6 e^{-} \to 2 Bi + 6 {OH}^{-}$

$3 {HSnO}_{2}^{-} (aq) + {Bi}_{2} O_{3} (s) + 6 H_{2} O + 3 {OH}^{-} (aq) \to 3 {[Sn {(OH)}_{6}]}^{2 -} (aq) + 2 Bi (s)$

$E_{cell} = E_{cell}^{\circ} - \frac{0.059}{6} \log (\frac{{(0.5)}^{3}}{{(0.05)}^{3} \times {[{OH}^{-}]}^{3}})$

$0.2353 = 0.46 - \frac{0.059}{6} \times 3 \log (\frac{10}{[{OH}^{-}]})$

$\log (\frac{10}{[{OH}^{-}]}) = \frac{2 \times 0.2247}{0.059} = 7.6$

$1 + pOH = 7.6$

$pOH = 6.6$

$pH = 14 - 6.6 = 7.4$

$pH = p K_{a 1} + \log \frac{[{HCO}_{3}^{-}]}{[H_{2} {CO}_{3}]}$

$7.4 = 6.11 + \log (\frac{5 x}{20})$

$1.29 = \log (\frac{x}{4})$

$\frac{x}{4} = 19.5$

$x = 78$

Solution

Want Us to Email you About Special Offers & Updates?