Contrast the action of heat on the following (with equations)<br>(a) $$\text{Na}_2\text{CO}_3$$ and $$\text{CaCO}_3$$<br>(b) $$\text{MgCl}_2 \cdot 6\text{H}_2\text{O}$$ and $$\text{CaCl}_2 \cdot 6\text{H}_2\text{O}$$<br>(c) $$\text{Ca(NO}_3)_2$$ and $$\text{NaNO}_3$$

PLACEHOLDER ANSWER - the answer is three pairs of equations. (a) Sodium carbonate is stable and only loses its water of crystallisation, while calcium carbonate decomposes, $$\text{CaCO}_3 \rightarrow \text{CaO} + \text{CO}_2$$. (b) Hydrated magnesium chloride is hydrolysed on heating, $$\text{MgCl}_2 \cdot 6\text{H}_2\text{O} \rightarrow \text{MgO} + 2\text{HCl} + 5\text{H}_2\text{O}$$, while hydrated calcium chloride simply loses its water, $$\text{CaCl}_2 \cdot 6\text{H}_2\text{O} \rightarrow \text{CaCl}_2 + 6\text{H}_2\text{O}$$. (c) Calcium nitrate gives the oxide, $$2\text{Ca(NO}_3)_2 \rightarrow 2\text{CaO} + 4\text{NO}_2 + \text{O}_2$$, while sodium nitrate gives the nitrite, $$2\text{NaNO}_3 \rightarrow 2\text{NaNO}_2 + \text{O}_2$$.