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Percentage of CaCO3 in a sample

Submitted by Lily on Wed, 07/27/2011 - 12:06

Calculate the percentage of CaCO3 in a 5.000g sample of limestone if 24.24mL of 2.500 M HCl is required to react completely with the CaCO3. Assume the rest of the limestone sample is inert.


Please help me understand how to set this up. Thank you

Find moles HCl by molarity x volume in litres

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

1mol             2mole

From moles of HCl in the first line, you know moles CaCO3 will be twice this.

From this and that 1 mole of CaCO3 has a mass of 100g  (40 + 12 + 16x3 or use the atomic masses in your course) find the mass of CaCO3 in your 5.000g sample.

%CaCO3 = (mass of CaCO3/5.000) x 100