# 7. A student conducts an experiment on a different hydrate. The empty crucible is heated to a constant

mass of 24.330. A sample of the unidentified hydrate is placed in the crucible, and the total mass is

31.571 g. The crucible and hydrate are heated to constant mass, which is measured at 29.002 g. The

molar mass of the anhydrous salt is 159.609 g.

a. Calculate the formula of this hydrate. Note that in the formula of a hydrate, salt•xH2O, the

coefficient “x” must be a whole number.

b. Give a reason your calculated value of “x” is less than the whole number to which you

rounded.

8. A student dehydrates a sample of magnesium sulfate heptahydrate. The anhydrous salt to water

ratio is 1:6.913. The correct formula is salt•7H2O.

a. Calculate the student’s percent error.

b. What is the physical meaning of the negative sign in the answer?