The formula of sodium carbonate is Na₂CO₃ and that of calcium hydrogen carbonate is

1. CaHCO₃
2. Ca(HCO₃)₂
3. Ca₂HCO₃
4. Ca(HCO₃)₃

Ca(HCO₃)₂

Reason — Chemical formula of calcium hydrogen carbonate:

$\text{Ca}^{2+} \space \text{HCO}$3^{1-} \\[1em] \overset{\phantom{22}{2}}{\text{Ca}} \space {\swarrow}\mathllap{\searrow} \space \overset{1}{\text{HCO}3} \Rightarrow \underset{\phantom{2}{1}}{\text{Ca}} \space {\swarrow}\mathllap{\searrow} \underset{\phantom{2}{2}}{\text{HCO}3} \\[1em] \text{Ca}\text{(HCO}3)_2

∴ Chemical formula of calcium hydrogen carbonate is Ca(HCO₃)₂