Download Important redox reactions involving concentrated nitric acid

Important redox reactions
involving concentrated nitric
acid
Concentrated nitric acid is a powerful
oxidizing agent. Please research the following chemical reactions so
that you are able to establish the important patterns in these redox
reactions. In each case justify the redox change by using oxidation
numbers. What has been oxidized and what has been reduced
1. the decomposition of concentrated nitric acid
4HNO3 -------------2H20 + 4NO2 + O2
Show any change in oxidation number
nitric acid has N ox number 5 this reduces to N ox number 4 in
nitrogen dioxide
2. concentrated nitric acid with copper (with explanation)
Cu + 4HNO3 ----------------Cu(NO3)2 + 2NO2 + 2H2O
Cu moves from ox 0 to ox +2, N in nitric acid partly drops from +5
to +4
3. Moderately concentrated nitric acid with copper (with
explanation)
3Cu + 8HNO3 --------------3Cu(NO3)2 + 4H2O + 2NO
Some of the N moves from +5 to +2, copper moves from 0 to +2
4 Concentrated nitric acid with sulphur (with explanation)
S + 6HNO3 ------------2H2O + 6NO2 + H2SO4
Here S jumps from 0 to +6, N from +5 to +4
5 Concentrated nitric acid with zinc (with explanation)
Zn + 4HNO3 ----------Zn(NO3)2 + 2NO2 + 2H2O
Zinc was 0 it becomes +2, some of the N moves from + 5 to +4
Redox Year 12. Reactions of concentrated nitric acid SOLUTIONS SHEET by HG
6 Concentrated nitric acid with carbon (with explanation)
C +4HNO3 -------------2H2O + 4NO2 + CO2
Here C was 0 it becomes +4, Nin nitric acid is +5 it drops to +4
again
Concentrated sulphuric acid can also act as an oxidizing agent. (It is
not as powerful as nitric acid) Dilute sulphuric acid does not with
copper metal. The concentrated acid does;
Cu + 2H2SO4 --------CuSO4 + 2H2O + SO2
Here copper was 0 it becomes +2 (hence oxidized) Sulphur in the
acid changes from +6 to +4 in sulphur dioxide
Patterns
When concentrated nitric acid undergoes redox change which gas is
usually produced?
Nitrogen Dioxide NO2
If concentrated sulphuric acid takes part in redox. Which gas is
most likely?
Sulphur Dioxide SO2
Redox Year 12. Reactions of concentrated nitric acid SOLUTIONS SHEET by HG