Question

five indigestion tablets containing calcium carbonate with a total mass of 2.50g were added to 50.0cm^3 of1.00mol dm^-3 hydrochloric acid.

CaCO3+2HCl--> CaCl2+CO2 +H2O

after reaction the solution was transferred to a 250cm^3 volumetric flask and the volume made up to 250cm^3 using deionised water. 25.0cm^3 samples of the solution were titrated against 0.126mol dm^-3 sodium hydroxide solution.

NaOH+HCl--> NaCl+H2O

the average titre was 11.30cm^3.

a) calculate the mass of calcium carbonate (in grams) in the five tablets.

give your answer to 3 significant figures.(AO2)

b) calculate the percentage of calcium carbonate in the tablets.(AO2)

Answer 1

Moles of $CaCO_3=\frac{2.50}{100.0869}=0.025 moles$

Moles of $HCl=2×0.025=0.05moles$

Mass in the five tablets = 2.50 grams

Moles of HCl$=1.00×\frac{50.0}{1000}=0.05$