ibo.org
Updates to Questionbank

User interface language: English | Español

« Back to questions in DP Chemistry

Date November 2009 Marks available 2 Reference code 09N.3.sl.TZ0.C4
Level SL Paper 3 Time zone TZ0
Command term Deduce and State Question number C4 Adapted from N/A

Question

Rechargeable nickel-cadmium batteries are used in portable electrical equipment and emergency lighting.

The discharge process can be summarized by the equation below.

\[{\text{2NiO(OH)(s)}} + {\text{Cd(s)}} + {\text{2}}{{\text{H}}_{\text{2}}}{\text{O(l)}} \rightleftharpoons {\text{2Ni(OH}}{{\text{)}}_{\text{2}}}{\text{(s)}} + {\text{Cd(OH}}{{\text{)}}_{\text{2}}}{\text{(s)}}\]

State the change in oxidation number of the cadmium and deduce if it is acting as the positive or negative electrode during the discharge process.

[2]
a.

Identify a physical property of Cd(OH)2 which allows this process to be reversed and the battery recharged.

[1]
b.

Markscheme

\(0 \to  + 2\) / increase by 2;

negative;

If decrease by 2, positive, award [1]. If decrease by 2, negative, award [0].

a.

insoluble (\({\text{C}}{{\text{d}}^{2 + }}\) ions do not escape into solution);

Do not accept solid.

b.

Examiners report

Most candidates were able to identify the change of oxidation number of cadmium but very few identified the insolubility of cadmium hydroxide as the physical property which allows the process to be reversed.

a.

Most candidates were able to identify the change of oxidation number of cadmium but very few identified the insolubility of cadmium hydroxide as the physical property which allows the process to be reversed.

b.

Syllabus sections

Core » Topic 9: Redox processes » 9.1 Oxidation and reduction
Show 165 related questions
Hide related questions

View options

Ib logo tri med

© International Baccalaureate Organization 2018
International Baccalaureate® - Baccalauréat International® - Bachillerato Internacional®

Printed for IB Documents Team