Quiz - PRELAB: Formula for a Hydrate

What information is necessary to determine the percentage of water in your hydrate sample?

• The mass of the anhydrous (dehydrated) compound

• The color of the unknown hydrate

• The temperature of the environment

• The volume of water used to cool the salt

How will the water be removed from the hydrate in this experiment?

• By freezing the hydrate

• By heating the hydrate

• By dissolving the hydrate in water

• By crushing the hydrate

A hydrate has the formula of MgSO₄·7H₂O. What is the percent by mass of water in this hydrate?

• 51.2%

• 48.8%

• 56.0%

• 44.2%

• Cannot be calculated

Considering lab safety, which statement best describes how you should treat this setup?

• assume all parts are hot

• assume the crucible is safe to touch after 1 minute

• assume the flame will go out on its own

• assume the clay triangle is safe to touch

• none of the above

How do you know when you have done enough trials?

• When 2 consecutive weights are equal/within uncertainty

• When 5-6 samples have been heated strongly

• When steps 1-3 no longer require gentle heating

• When the masses are all the same

• None of these

What is a hydrate?

• a water compound with salt attached to it

• a salt compound

• a salt compound with water in its crystalline structure

• an electrolyte

• none of these

What is the purpose of slightly opening the crucible lid (cover)?

• To prevent splatter

• To see when the reaction is done

• To see when the dehydration is done

• To let steam (gas) out

• None of these