Reaction between ethanol, sulfuric acid and potassium dichromate

Experiment

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Redox reactions

- First step: Ethanol $\Rightarrow$ ethanal: $CH_3CH_2OH$ $-$ $2e^-$ $\rightarrow$ $ CH_3CHO$ $+$ $2H^+$ | $\cdot 3$ $Cr_2O_7^{2-}$ $+$ $6e^-$ $+$ $14H^+$ $\rightarrow$ $ 2Cr^{3+}$ $+$ $7H_2O$ $3CH_3CH_2OH$ $+$ $Cr_2O_7^{2-}$ $ +$ $8H^+$ $\rightarrow$ $ 3CH_3CHO $ $+$ $ 2Cr^{3+}$ $+$ $7H_2O$ - Second step: Ethanal $\Rightarrow$ ethanoic (acetic) acid: $CH_3CHO-2e^-$ $+$ $H_2O$ $\rightarrow$ $ CH_3COOH$ $+$ $2H^+$ | $\cdot 3$ $Cr_2O_7^{2-}$ $+$ $6e^-$ $+$ $14H^+$ $\rightarrow$ $ 2Cr^{3+}$ $+$ $7H_2O$ $3CH_3CHO$ $+$ $Cr_2O_7^{2-}$ $ +$ $8H^+$ $\rightarrow$ $ 3CH_3COOH$ $ + $ $2Cr^{3+}$ $+$ $4H_2O$

A color change from orange $(Cr_2O_7^{2-})$ to dark green $(Cr^{3+})$ is observed.