Analytical analysis

in an experiment to determine amount of calcium carbonate purity.100 cubic centimeters of 1 molar hydrochloric acid solution were added to 15 gram of finely ground chalk,the solution was warmed slowly to ensure that the carbon iv oxide evolved was driven off.the solution was then diluted to 250 cubic centimeters.a 25 cubic centimeters aliquot was titrated against 0.1molar sodium hydroxide using phenolphthalein indicator.the average titre was 22.3cubic centimeters.calculate the Percentage purity of the sample