Question

Calculate (a) the moles and (b) the mass of magnesium carbonate at the start if 0.2 moles of sulfuric acid is added to the magnesium carbonate and the excess sulfuric acid made up to a 250 cm3 solution. 25 cm3 of this solution required 0.03 moles of sodium hydroxide for neutralisation.

MgCO3 + H2SO4 ¨ MgSO4 + H2O + CO2 H2SO4 + 2

NaOH ¨ NaCl + H2O

Answer 1

the actual mass (g) = Number of moles x Molar mass,
or m = n x M

Number of moles of solute = Concentration (mol. L) x Volume of solution (liters) -1
or n = C x V

Answer 2

The question is wrong by the way, the product of H2SO4 reacting with 2 NaOH should be Na2SO4 + 2 H2O