A hydrate of sodium acetate, NaC2H3O2, has a mass of 84g. Upon dehydration 39.27g of water is extracted from the compound. What is the Formula of the compound?

First, change the 39.27grams of water to moles using the molar mass.

Molar mass H2O = 18.02 grams/mole

39.27 grams x (1 mole H2O / 18.02 grams) = 2.18 moles

The mass of sodium acetate can be calculated by subtracting the mass of the compound minus the mass of water.

84 g - 39.27 grams = 44.73 grams

Now change does to moles using the molar mass

Molar mass of sodium acetate = 82 g / mol

44.73 g x (1 mole / 82 grams) = 0.545 mole

Now divide the both value by the smallest.

H2O - 2.18 / 0.545 = 4

sodium acetate = 0.545 / 0.545 = 1

The formula is NaC2H3O2 • 4 H2O