Question

Sam records the mass of his evaporating dish as 6.251 g.

Answer 1

Answer:

• 0.318 moles

Explanation:

1. Mass of water removed

• Mass of water removed = mass of the evaporating dish and the sample of hydrate - mass of the evaporating dish and the sample after heating

• Mass of water evaporated =  16.864 g - 11.13 g = 5.734 g

This amount must be rounded to two decimals, because the least precise measure (11.13 g) contains two decimals.

• Mass of water evaporated = 5.73 g

2. Moles of water removed from the sample by the heating process

You must use the molar mass of water to convert 5.73 g of water to number of moles.

• Molar mass of water: 18.015 g/mol

• Number of moles = mass in grams / molar mass = 5.73 g / 18.015 g/mol = 0.318 moles.