Q.(i) Complete the following reaction: KMnO4 --513 K--> ?

KMnO$_4$ decomposes thermally to give K$_2$MnO$_4$, MnO$_2$ and O$_2$; the orange-red fumes from NaCl + dichromate + H$_2$SO$_4$ are chromyl chloride; actinoid contraction is larger because 5f electrons shield poorly.

(i) Thermal decomposition of potassium permanganate:

$2KMnO_4 \xrightarrow{513\,K} K_2MnO_4 + MnO_2 + O_2\uparrow$

(ii) Heating NaCl with potassium dichromate and concentrated H$_2$SO$_4$ produces orange-red vapours of chromyl chloride, CrO$_2$Cl$_2$:

$4NaCl + K_2Cr_2O_7 + 6H_2SO_4 \xrightarrow{\Delta} 2CrO_2Cl_2\uparrow + \ldots$

This reaction (giving reddish-orange fumes/liquid) is the basis of the "chromyl chloride test" used to confirm chloride ions.

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