Question

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?

Answer 1

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