Question

A carbonate which do not decompose on heating is :

• A. magnesium carbonate
• B. zinc carbonate
• C. potassium carbonate
• D. calcium carbonate

Answer 1

The correct option is C

potassium carbonate

Explanation for correct options-

Sodium carbonate(NaNO₃) and Potassium carbonate(KNO₃) are the two carbonates that do not decompose on heating.

Explanation for incorrect options-

• At high temperatures Magnesium carbonate (MgCO₃) decomposes to magnesium oxide(MgO)) and carbon dioxide(CO₂).

$\underset{\mathrm{Magnesium}\mathrm{carbonate}}{{\mathrm{MgCO}}_3}\to \underset{\mathrm{Magnesium}\mathrm{oxide}}{\mathrm{MgO}}+\underset{\mathrm{Carbon}\mathrm{dioxide}}{{\mathrm{CO}}_2}$

• Calcium carbonate(CaCO₃) decomposes on heating to form calcium oxide(CaO) and carbon dioxide(CO₂).

$\underset{\mathrm{Calcium}\mathrm{carbonate}}{{\mathrm{CaCO}}_3}\to \underset{\mathrm{Calcium}\mathrm{oxide}}{\mathrm{CaO}}+\underset{\mathrm{Carbon}\mathrm{dioxide}}{{\mathrm{CO}}_2}$

• Zinc carbonate(ZnCO₃) on heating decomposes to zinc oxide(ZnO) and carbon dioxide(CO₂).

$\underset{\mathrm{Zinc}\mathrm{carbonate}}{{\mathrm{ZnCO}}_3}\stackrel{∆}{\to }\underset{\mathrm{Zinc}\mathrm{oxide}}{\mathrm{ZnO}}+\underset{\mathrm{Carbon}\mathrm{dioxide}}{{\mathrm{CO}}_2}$

Thus, among the given options (C) potassium carbonate is the correct answer.