1.5 g of chalk was treated with 10 " mL of " 4 N HCl. The chalk was dissolved and the solution was made to 100 mL. 25 " mL of " this solution required 18.75 mL of 0.2 N NaOH solution for comjplete neutralisation. Calculate the percentage of pure `CaCO_3` in the sample of chalk.

Explanation

To calculate the percentage of pure CaCO₃ in the sample of chalk, we will follow these steps:

### Step 1: Calculate the moles of HCl used
Given:
- Normality (N) of HCl = 4 N
- Volume (V) of HCl = 10 mL = 0.010 L

Using the formula:
...