Question

Consider the titration of 25.0 mL of 0.01000 M Sn²⁺ by 0.0500 M Tl³⁺ in 1 M HCl, using Pt and saturated calomel electrodes to find the endpoint.

a.) Write the balanced titration reaction.

b.) Write two different half-reactions for the indicator electrode.

$Sn^{4+}+2e^{-}\rightleftharpoons Sn^{2+}$

$Tl^{3+}+2e^{-} \rightleftharpoons Tl^{+}$

c.) Write two different Nernst equations for the cell voltage.

d.) Calculate E at the following volumes of Tl³⁺: 1.00, 2.50, 4.90, 5.00, 5.10, and 10.0 mL.

(This is problem 3 in Chapter 15 from Eigth Edition of the Quantitative Chemical Analysis Textbook by Harris)

Answer 1

a) b) s_n^2 + rightarrow 0.01 M T l^3 + rightarrow 0.05 M . Rightarrow S_n^4 + + 2 e^- rightarrow S_n^2 + E degree = 0.139 V T l^3 + - 2 e^- rightarrow T l^+ E^0 = 0.77 V/S_n^2 + + T l^3 + rightarrow S_n^4 + + T l^+ (n = 2) Rightarrow E = E^+ - E^- (calomel) E = E degree - 0.0591/n 10 g - 0.241 downarrow calomel potential Rightarrow E = 0.139 - 0.059/2 log [s_n^2 + /(s_n^4 +] - 0.241 Rightarrow E = 0.77 - 0.059/2 log [T l &^+]/[T l^2 +] - 0.241 Rightarrow for l m l, v e