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Date November 2014 Marks available 3 Reference code 14N.3.hl.TZ0.24
Level HL Paper 3 Time zone TZ0
Command term Deduce Question number 24 Adapted from N/A

Question

In an acidic soil, nitrate ions may undergo reduction to form ammonium ions. Deduce a half-equation for the reaction.

Markscheme

\({\text{NO}}_3^ -  + {\text{10}}{{\text{H}}^ + } + {\text{8}}{{\text{e}}^ - } \to {\text{NH}}_4^ +  + {\text{3}}{{\text{H}}_2}{\text{O}}\)

correct reactants;

correct products;

correct balancing;

M3 can only be scored if M1 and M2 correct.

Examiners report

The equation caused some difficulty for many students; electrons were omitted on the left-hand side, incorrect products were given and equations were left unbalanced.

Syllabus sections

Core » Topic 9: Redox processes » 9.1 Oxidation and reduction
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