practical questions

Question 1

It is difficult to ensure consistency with the setup of a standard hydrogen electrode.
A Cu2+(aq)/Cu(s) electrode (Eo = +0.34 V) can be used as a secondary standard.
A student does an experiment to measure the standard electrode potential for the
TiO2+(aq)/Ti(s) electrode using the Cu2+(aq)/ Cu(s) electrode as a secondary
standard.
A suitable solution containing the acidified TiO2+(aq) ion is formed when
titanium(IV) oxysulfate (TiOSO4) is dissolved in 0.50 mol dm−3 sulfuric acid to make
50 cm3 of solution.
0 6 . 2 Describe an experiment the student does to show that the standard electrode
potential for the TiO2+(aq)/Ti(s) electrode is −0.88 V
The student is provided with:
* the Cu2+(aq)/ Cu(s) electrode set up ready to use
* solid titanium(IV) oxysulfate (Mr = 159.9)
* 0.50 mol dm−3 sulfuric acid
* a strip of titanium
* laboratory apparatus and chemicals.
Your answer should include details of:
* how to prepare the solution of acidified TiO2+(aq)
* how to connect the electrodes
* measurements taken
* how the measurements should be used to calculate the standard electrode potential
for the TiO2+(aq)/Ti(s) electrode.

Answer 1

Stage 1 Preparing solution
(1a) Weigh 7.995 / 8.00 g TiOSO4
(1b) Dissolve in / add (allow react with) (0.50
moldm-3
) sulfuric acid
(1c) transfer to volumetric flask and make up to
the mark
Stage 2 Set up cell
Content can be shown in a labelled diagram
(2a) piece of Ti immersed in (1 mol dm−3 acidified)
TiO2+(aq) / the solution
(2b) (connect solutions with) salt bridge or
description
(2c) (connect metals through high R) voltmeter
Stage 3 measurements and calculation
(3a) record voltage/potential difference/emf of the
cell
(3b) Ecell = ERHS – ELHS
Ecell = Ecopper – Etitanium
(3c) ELHS = ERHS – Ecell OR Ecell should be +1.22 V
if Cu on RHS (or −1.22 if Cu electrode on
LHS)