A 5-g sample of impure magnesium carbonate is reacted with an excess of hydrochloric acid: MgCO3 (s) 1 2HCl (aq) MgCl2 (aq) 1 H2O (l) 1 CO2 ( g) 1250 cm3 of carbon dioxide is collected at rtp. a How many moles of CO2 are produced? b What mass of pure magnesium carbonate would give this volume of carbon dioxide? (Ar : C 5 12, O 5 16, Mg 5 24.) c Calculate the % purity of the 5-g sample.​