Solution

Step 1 - Work out the equations for all the reactions taking place.

The equation for
the reaction between HCl with the limestone is given below.

Equation 1

The equation for
the reaction between HCl and sodium carbonate is given below.

Equation 2

Step 2 - From equation 2 we can work out the mole of HCl left unreacted.

Step 3 - Work out how much HCl did react. Subtract the amount in excess from the amount originally added.

Amount originally
added - amount in excess = amount reacted.

(0.1 X 1.1) - 0.0602 = 0.0498 mole of HCl reacted.

Step 3 - Using equation
1 calculate the amount of caclium carbonate present.

Mole of HCl /2 = mole of calcium carbonate = 0.0498/2 = 0.0249 mole.

Step 4 - Calculate the mass of calcium carbonate present.

0.0249 X formula mass
= 0.0249 X 100 = 2.49 grams

Step 4 Calculate the
percentage

2.49/3.00 X100 = 83.0%