Question: When ammonia is added to the solution, pH is raised to 11 . Which half | TestHub

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Paragraph:Tollen's reagent is used for the detection of aldehyde when a solution of $AgNO_{3}$ is added to glucose with $NH_{4} OH$ then gluconic acid is formed $Ag^{+} + e^{-} \to Ag C_{6} H_{12} O_{6} + H_{2} O \to Gluconic acid (C_{6} H_{12} O_{7}) + 2 H^{+} + 2 e^{-}; Ag (NH_{3})_{2}^{+} + e^{-} \to Ag (s) + 2 NH_{3}; E_{red}^{\circ} = 0.8 V - E_{red}^{\circ} = - 0.05 V E_{red}^{\circ} = 0.337 V$ [Use $2.303 \times \frac{RT}{F} = 0.0592$ and $\frac{F}{RT} = 38.92$ at $298 K$ ]

Question:When ammonia is added to the solution, $pH$ is raised to 11 . Which half-cell reaction is affected by $pH$ and by how much?

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Answer:

C

Solution:

On increasing concentration of $NH_{3}$ , the concentration of $H^{+}$ ion decreases, therefore $E_{red} = E_{red}^{\circ} - \frac{0.0592}{n} lo g_{10} [H^{+}]^{2} = 0 - \frac{0.0592}{2} \times 2 lo g_{10} 1 0^{- 11} (∵ pH = 11; ∴ [H^{+}] = 1 0^{- 11} M) = - 0.0592 \times 11 = 0.6512 V = 0.65 V$ $E_{red}$ increased by a factor of $0.65$ from $E_{red}^{\circ}$ .

Stream:JEE_ADVSubject:ChemistryTopic:ElectrochemistrySubtopic:Galvanic cells/Nernst Equation/Concentration Cells

⏱ 2mℹ️ Source: PYQ_2006

Chemistry - Electrochemistry Question with Solution | TestHub

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