(a) What is the change in oxidation state of chromium in the reaction represented by...
(a) What is the change in oxidation state of chromium in the reaction represented by the following equation?
3SO\(_2\) + Cr\(_2\)O\(^2_{-7}\) + 2H\(^+\) -> 3SO\(_4^{2-}\) + 2Cr\(^{3+}\) + H\(_2\)O
(b) Use the half equations given below to deduce the equation for the reaction between iron(II) ions and heptaoxodichromate (VI) ions in acidic solution.
Fe\(^{2+}\) --> Fe\(^{3+}\) + e\(^-\)
Cr\(_2\)O\(^{2-}_7\) + 14H\(^+\) + 6e\(^-\) ----> 2Cr\(^{3+}\) + 7H\(_2\)O.
Explanation
(a) From +6 to +3
(b) The reaction involves the transfer of 6 electrons from 6Fe 2+ to Cr\(_2\)O\(_7\)
SO, 6Fe\(^{2+}\) \(\rightleftharpoons\) 6Fe\(^{3+}\) + 6e\(^-\)
The addition of the 2 half cell equations gives Cr\(_2\)O\(_7^{2-}\) + 14H\(^+\) — 6Fe\(^{2+}\) \(\to\) 2Cr\(^{3+}\) + 6Fe\(^{3+}\) + 6Fe\(^{3+}\) + 7H\(_2\)O.