Hydrates and Molar Mass Calculations

Melanie Fine from Chemin 10 explains how to determine the percent of water in a hydrate, using barium hydroxide octahydrate as an example. The process involves calculating the molar mass of water and the entire compound, then using these values to find the water percentage. The video concludes with a final calculation showing that the water content is 45.7%.

What is a hydrate?

• A compound with water molecules bound to it

• A compound without any water

• A compound that evaporates quickly

• A compound that is always dry

What is the first step in determining the percent of water in a hydrate?

• Determine the volume of the compound

• Find the density of the compound

• Calculate the mass of water in the compound

• Calculate the mass of the entire compound

How do you calculate the mass of water in barium hydroxide octahydrate?

• Add the number of water molecules to the molar mass of water

• Divide the number of water molecules by the molar mass of water

• Multiply the number of water molecules by the molar mass of water

• Subtract the number of water molecules from the molar mass of water

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

• 16.02 grams per mole

• 22.02 grams per mole

• 20.02 grams per mole

• 18.02 grams per mole

What is the molar mass of barium used in the calculation?

• 139.33 grams per mole

• 135.33 grams per mole

• 140.33 grams per mole

• 137.33 grams per mole

How many moles of hydroxide are in barium hydroxide?

• One mole

• Four moles

• Three moles

• Two moles

What is the total mass of barium hydroxide octahydrate?

• 320.51 grams per mole

• 325.51 grams per mole

• 310.51 grams per mole

• 315.51 grams per mole

What is the final percent of water in barium hydroxide octahydrate?

• 45.7%

• 50.7%

• 55.7%

• 40.7%

What is the purpose of multiplying by 100 in the final calculation?

• To adjust for molar mass

• To simplify the calculation

• To increase the accuracy

• To convert the ratio to a percentage

Where can you get more stoichiometry help according to the video?

• moleproblems.com

• chemistry101.com

• stoichhelp.com

• purplestoic.com