Hydrates and Their Properties

Melanie Fine explains how to determine the formula of a hydrate. A hydrate is a molecule with water bound to it. The process involves heating to remove water, measuring mass differences, and converting these masses to moles. A sample problem with magnesium sulfate is used to illustrate the steps: calculating the mass of water driven off, converting masses to moles, and determining the ratio of the anhydrate to water. The video concludes with the hydrate being identified as magnesium sulfate heptahydrate.

What is a hydrate?

• A molecule with oxygen bonded to it

• A molecule with water bonded to it

• A molecule with hydrogen bonded to it

• A molecule with carbon bonded to it

What is the first step in determining the formula of a hydrate in the lab?

• Add more water

• Drive off the water by heating

• Measure the temperature

• Cool the sample

In the sample problem, what is the mass of the magnesium sulfate after the water is driven off?

• 12.37 grams

• 13.52 grams

• 6.92 grams

• 6.60 grams

How do you calculate the mass of water driven off in the sample problem?

• Divide the mass of the hydrate by the anhydrate

• Multiply the mass of the hydrate by the anhydrate

• Subtract the mass of the anhydrate from the hydrate

• Add the mass of the hydrate and anhydrate

What is the molar mass of water used in the calculations?

• 13.52 grams

• 18.016 grams

• 12.37 grams

• 6.60 grams

How many moles of magnesium sulfate are present in 6.60 grams?

• 2.0 moles

• 0.548 moles

• 1.0 moles

• 0.384 moles

What is the ratio of magnesium sulfate to water in the hydrate?

• 1:7

• 1:6

• 1:8

• 1:5

What prefix is used to indicate seven molecules of water in a hydrate?

• Hexa

• Octa

• Nona

• Hepta

What is the final formula of the hydrate in the sample problem?

• Magnesium sulfate monohydrate

• Magnesium sulfate dihydrate

• Magnesium sulfate heptahydrate

• Magnesium sulfate hexahydrate

What is the purpose of dividing by the smallest number in the mole ratio calculation?

• To simplify the ratio to whole numbers

• To find the largest ratio

• To increase the number of moles

• To decrease the number of moles