Formulae, equations and amount of substance

Moles, empirical and molecular formulae, balanced equations, concentrations, gas volumes and yields.

A student adds $2.50\,\text{g}$ of calcium carbonate to $50.0\,\text{cm}^3$ of $2.00\,\text{mol dm}^{-3}$ hydrochloric acid.

$\text{CaCO}_3(\text{s}) + 2\text{HCl}(\text{aq}) \rightarrow \text{CaCl}_2(\text{aq}) + \text{H}_2\text{O}(\text{l}) + \text{CO}_2(\text{g})$

(a) Show by calculation that the hydrochloric acid is in excess.

(b) Calculate the volume of carbon dioxide produced, in $\text{dm}^3$ , at room temperature and pressure.

[ $M_r$ of $\text{CaCO}_3 = 100.1$ ; molar volume of a gas at RTP $= 24.0\,\text{dm}^3\,\text{mol}^{-1}$ ]

$n(\text{CaCO}_3) = 2.50 \div 100.1 = 0.0250\,\text{mol}$ (1)
$n (HCl) = 0.0500 \times$ , which is more than the needed, so HCl is in excess (1)

A compound contains only carbon, hydrogen and oxygen. By mass it is $54.5\%$ carbon and $9.1\%$ hydrogen. Its relative molecular mass is $88.0$ .

Calculate the empirical formula and hence deduce the molecular formula of the compound.

Specification points