Question

15.67 g sample of a hydrate of magnesium carbonate was heated, without decomposing the carbonate, to

drive off the water. The mass was reduced to 7.58 g. What is the formula of the hydrate? Name the hydrate

Answer 1

Problem #1: A 15.67 g sample of a hydrate of magnesium carbonate was heated, without decomposing the carbonate, to drive off the water. The mass was reduced to 7.58 g. What is the formula of the hydrate? Solution: 1) Determine mass of water driven off: 15.67 minus 7.58 = 8.09 g of water 2) Determine moles of MgCO3 and water: MgCO3 --> 7.58 g / 84.313 g/mol = 0.0899 mol H2O --> 8.09 g / 18.015 g/mol = 0.449 mol 3) Find a whole number molar ratio: MgCO3 --> 0.0899 mol / 0.0899 mol = 1 H2O --> 0.449 mol / 0.0899 mol = 5 MgCO3 · 5H2O

Answer 2