Boiling of hard water is helpful in removing the temporary hardness by converting calcium hydrogen carbonate and magnesium hydrogen carbonate to

We need to determine the products formed when temporary hard water is boiled.

Temporary hardness is caused by the presence of calcium hydrogen carbonate $$Ca(HCO_3)_2$$ and magnesium hydrogen carbonate $$Mg(HCO_3)_2$$.

For calcium hydrogen carbonate:

$$Ca(HCO_3)_2 \xrightarrow{\Delta} CaCO_3 \downarrow + H_2O + CO_2 \uparrow$$

Calcium hydrogen carbonate decomposes to give insoluble calcium carbonate.

For magnesium hydrogen carbonate:

$$Mg(HCO_3)_2 \xrightarrow{\Delta} Mg(OH)_2 \downarrow + 2CO_2 \uparrow$$

Magnesium hydrogen carbonate, on prolonged boiling, gives magnesium hydroxide (not magnesium carbonate), because $$MgCO_3$$ is more soluble and further decomposes.

The products are $$CaCO_3$$ and $$Mg(OH)_2$$.

The correct answer is Option A: $$CaCO_3$$ and $$Mg(OH)_2$$.