Question
Which of the following does not give oxygen on heating?
A.
$$KCl{O_3}$$
B.
$$Zn{\left( {Cl{O_3}} \right)_2}$$
C.
$${K_2}C{r_2}{O_7}$$
D.
$${\left( {N{H_4}} \right)_2}C{r_2}{O_7}$$
Answer :
$${\left( {N{H_4}} \right)_2}C{r_2}{O_7}$$
Solution :
Oxygen rich compounds like chlorate, perchlorate, $${K_2}C{r_2}{O_7},$$ etc. when heated gives oxygen but ammonium dichromate gives nitrogen gas when heated.
\[\begin{align}
& 2KCl{{O}_{3}}\xrightarrow{\Delta }2KCl+3{{O}_{2}}\uparrow \\
& 2Zn{{\left( Cl{{O}_{3}} \right)}_{2}}\xrightarrow{\Delta }ZnC{{l}_{2}}+3{{O}_{2}} \\
\end{align}\]
\[\underset{\begin{smallmatrix}
\text{Potassium} \\
\text{dichromate}
\end{smallmatrix}}{\mathop{4{{K}_{2}}C{{r}_{2}}{{O}_{7}}}}\,\xrightarrow{\Delta }\underset{\begin{smallmatrix}
\text{Potassium} \\
\text{chromate}
\end{smallmatrix}}{\mathop{4{{K}_{2}}Cr{{O}_{4}}}}\,\] \[+\underset{\begin{smallmatrix}
\text{Chromic} \\
\text{oxide}
\end{smallmatrix}}{\mathop{2C{{r}_{2}}{{O}_{3}}}}\,+3{{O}_{2}}\uparrow \]
\[{{\left( N{{H}_{4}} \right)}_{2}}C{{r}_{2}}{{O}_{7}}\xrightarrow{\Delta }\] \[{{N}_{2}}\uparrow C{{r}_{2}}{{O}_{3}}+4{{H}_{2}}O\]