Calculate the mass of solid A and the molar mass of Na2S2O3 * 5H2O.

Here are the solutions to the questions:

QUESTION ONE

• Mass of solid A: Mass of weighing bottle + solid A = 18.23 g Mass of weighing bottle alone = 12.00 g Mass of solid A = $18.23 \text{ g} - 12.00 \text{ g} = \boxed{6.23 \text{ g}}$

• Molar mass of $\text{Na}_2\text{S}_2\text{O}_3 \cdot 5\text{H}_2\text{O}$: $\text{Na}: 2 \times 22.99 = 45