Final answer:
To find the formula for the hydrate of calcium sulfite containing 23.1% water by mass, we calculate the molar ratio of water to calcium sulfite. The calculations show that there are approximately two moles of water for every mole of calcium sulfite, indicating that the hydrate is calcium sulfite dihydrate (CaSO3 · 2H2O), which corresponds to option B.
Step-by-step explanation:
To determine the formula and name of the hydrate of calcium sulfite with 23.1% water by mass, we need to use the mass percentages of water and the molar masses of the compounds involved. The molar mass of water (H2O) is approximately 18.015 g/mol, and the molar mass of calcium sulfite (CaSO3) is approximately 120.17 g/mol. To find out how many moles of water correspond to 23.1% by mass in the hydrate, we use the proportion:
(Mass of water / Molar mass of H2O) : (Mass of CaSO3 / Molar mass of CaSO3) = 23.1% : (100% - 23.1%)
Let's assign 100 g as the total mass of the hydrate for ease of calculation. This means we have 23.1 g of water and 76.9 g of calcium sulfite. Dividing the mass of each by its respective molar mass gives us:
(23.1 g / 18.015 g/mol) : (76.9 g / 120.17 g/mol) = moles of water : moles of CaSO3
After calculating, we find that the ratio of moles of water to moles of CaSO3 is approximately 2:1, meaning there are about two moles of water for every mole of calcium sulfite. Therefore, the correct formula and name for this hydrate would be
CaSO
3
· 2H
2
O
(Calcium sulfite dihydrate), which corresponds to option B.