Final answer:
To find the mass of water in the hydrate, subtract the mass of the anhydrous residue (10.48 g) from the initial mass of the hydrate (15.67 g), resulting in 5.19 g of water lost. Option A: 5.19 g is the correct option.
Step-by-step explanation:
The mass of the water in the hydrate can be found by subtracting the mass of the anhydrous residue from the initial mass of the hydrate. Starting with a 15.67 g sample of hydrate, after heating, you have 10.48 g of anhydrous magnesium carbonate.
The mass of water lost would be the initial mass minus the mass of the anhydrous residue:
Mass of water = Initial mass of hydrate - Mass of anhydrous residue
Mass of water = 15.67 g - 10.48 g = 5.19 g
Therefore, Option A: 5.19 g is the mass of the water in the hydrate, and this will be our correct option in the final answer.