Question

Consider the titration of 50.0 mL of 0.0200 M In+ by 0.0500 m Cu2+ using Pt and

saturated calomel electrodes to find the end point.

a. Write a balanced titration reaction.

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

c. Write two different Nernst equations for the net cell reaction.

d. Calculate E at the following volumes of Cu2+: 1.00, 20.0, 39.0, 40.0, 41.0, and 80.0

mL. Sketch the titration curve.

2. Consider the titration of 50.0 mL of 0.0250 M Fe3+ by 0.0500 M Cu+ to give Fe2+ and Cu2+ ,

using Pt and saturated AgAgCl electrodes to find the end point.

a. Write a balanced titration reaction.

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

c. Write two different Nernst equations for the net cell reaction.

d. Calculate E at the following volumes of Cu2+: 1.0, 12.5, 24.5, 25.0, 25.5 and 30.0

mL. Sketch the titration curve 

Answer 1

1)

a)  Balanced titration reaction

$In^{+} + Cu^{2+}⇋ In^{2+}+Cu^+$

b) half-reaction

$In^{+} \rightarrow In^{2+}+ e^-$ E^o = 0.4 V

$Cu^{2+} + e^- \rightarrow Cu^+$ E^o = 0.161 V

c)Nernst equations for half reactions

$$E=0.4-0.059log({[In^{2+ }]\over[In^{+}]})$$

$$E=0.161-0.059log({[Cu^{+ }]\over[Cu^{2+}]})$$

2)

a)  Balanced titration reaction

$Fe^{3+} + Cu^+ \rightarrow Fe^{2+} + Cu^{2+}$

b)half-reaction

$Cu^{2+}+ e^- \rightleftharpoons Cu^+$ E^o = 0.161 V

$Fe^{3+}+ e^- \rightleftharpoons Fe^{2+}$ E^o = 0.767 V

c) Nernst equations for half reactions

$$E=0.767-0.059log({[Fe^{2+ }]\over[Fe^{3+}]})$$

$$E=0.161-0.059log({[Cu^{+ }]\over[Cu^{2+}]})$$