Question

Ammonium chromate on heating gives-
A. A green coloured compound
B. A colorless gas
C. Water vapours
D. All of the above

Answer 1

Hint: Ammonium chromate is a yellow or orange coloured salt. It forms yellow crystals. It is toxic in nature. It produces chromic oxide and nitrogen gas on heating along with water. It is a threat to the environment if it spreads in the environment.

Step-by-Step Solution-
Ammonium chromate is an orange coloured salt which has chemical formula ${\left( {{\text{N}}{{\text{H}}_4}} \right)_2}{\text{C}}{{\text{r}}_2}{{\text{O}}_7}$. It has following properties-
It smells like ammonia.
It is toxic in nature as its inhalation causes severe irritation and if ingested can cause stomach and kidney damage.
It is soluble in water but insoluble in ethanol and only slightly soluble in liquid ammonia and acetone
It ignites on heating and decomposes into chromic oxide, a nitrogen gas and water vapors. The reaction is given as-
${\left( {{\text{N}}{{\text{H}}_4}} \right)_2}{\text{C}}{{\text{r}}_2}{{\text{O}}_7}\xrightarrow{{heat}}{\text{C}}{{\text{r}}_2}{{\text{O}}_3}\left( {\text{s}} \right){\text{ + }}{{\text{N}}_2}\left( {\text{g}} \right){\text{ + 4}}{{\text{H}}_2}{\text{O}}\left( {\text{g}} \right)$
This is a thermal decomposition reaction as the compound decomposes into its components due to heating.
In this reaction, Chromic oxide is a green coloured compound where as nitrogen gas produced is a colourless gas. Also water is released in the form of vapours.
Hence all of the given options are produced in this reaction.

Answer-So the correct answer is D.

Note: The uses of Ammonium chromate are-
- It is used as a mordant in dyeing.
- It is used in photography in sensitizing gelatin.
- It is used in the textile industry and in fixing chromate dyes on wool.
- It is used in the manufacture of alizarin and chrome alum.
- It is used in oil purification and leather tanning.
- It is used as a corrosion inhibitor.