Chemistry · Electronic concepts of oxidation and reduction, redox reactions, oxidation number, rules for assigning oxidation number and balancing of redox reactions
When sodium hydroxide solution is added to a freshly prepared solution of ferrou
When sodium hydroxide solution is added to a freshly prepared solution of ferrous sulphate, a green precipitate of ferrous hydroxide is formed which on standing turns brown because:
- A. ferric salts are unstable
- B. the mixture becomes dirty
- C. ferrous hydroxide becomes ferric oxide
- D. green ferrous hydroxide oxidises to brown ferric hydroxide
Step-by-step solution
When NaOH is added to FeSO4 solution, a green precipitate of Fe(OH)2 forms. Fe(OH)2 is unstable in air and gets oxidized by atmospheric oxygen to brown Fe(OH)3. This is a redox reaction where Fe(II) is oxidized to Fe(III).
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