A household cleaning agent contains a weak base with the formula NaX - HSC - SSCE Chemistry - Question 18 - 2011 - Paper 1

From the reaction of the weak base (NaX) with hydrochloric acid, we assume it reacts in a 1:1 ratio. Therefore, the moles of the weak base in the 20.0 mL sample is also 0.00244 mol.

Since 20.0 mL is only a part of the 100.0 mL total solution, we need to find the total moles of the weak base dissolved in the entire solution:

$\text{Total moles of weak base} = \text{Moles in sample} \times \frac{100.0 \text{ mL}}{20.0 \text{ mL}} = 0.00244 \text{ mol} \times 5 = 0.0122 \text{ mol}$

Now we can calculate the molar mass (M) of the weak base using the formula:

$M = \frac{\text{Mass}}{\text{Moles}}$

We have a mass of 1.00 g of the weak base dissolved, which corresponds to 0.0122 mol:

$M = \frac{1.00 \text{ g}}{0.0122 \text{ mol}} \approx 82.0 \text{ g/mol}$