Question
- What happens when $H_2O_2$ is passed through alkaline solution of Chromium sulphate? Write the chemical reaction involved.
- Compare the structures of $H_2O$ and $H_2O_2$.
✓
Answer
- The solution will become yellow in colour due to formation of $Na_2CrO_4$.
Alternate Answer
$2\text{Cr}^3+3\text{H}_2\text{O}_2+10\text{OH}^-\xrightarrow{\ \ \ \ \ \ \ \ \ }2\text{Cr}\text{O}_4^{2-}+8\text{H}_2\text{O}$
- Structure of $H_2O$ and $H_2O_2$:
In $\mathrm{H}_2 \mathrm{O}$, O is $\mathrm{sp}^3$ hybridised but due to lone pair-lone pair repulsion, the HOH bond angle decreases to $104.5^{\circ}$. Hence, water is a bent molecule as shown above.
In $\mathrm{H}_2 \mathrm{O}_2$, the two oxygen atoms are linked to each other by single bond (peroxide) and each oxygen is further linked to H atom by single bond. The two $\mathrm{O}-\mathrm{H}$ bonds are in different plane, giving $\mathrm{H}_2 \mathrm{O}_2$ a non-planar structure as shown above.
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