A sample of MgCO3•3H2O (magnesium carbonate trihydrate) is heated until 40.37 grams of water are released. How many grams did the original hydrate weigh?

Answer:-

103.168 grams

Explanation:-

When a hydrate salt is heated water is released and anhydrous salt is formed.

The balanced Chemical equation for the reaction is

MgCO3.3H2O - -> MgCO3 + 3H2O

Molecular mass of MgCO3.3H2O = 24 x 1 + 12 x 1 + 16 x 3 + 3 x (1 x 2 + 16 x 1)

= 138 gram

Molecular mass of H2O = 1 x 2 + 16 x 2 = 18 gram

From the balanced chemical equation

3 H2O is released from 1 MgCO3.3H2O.

∴ 3 x 18 gram of H2O is released from 138 gram of MgCO3.3H2O.

40.37 gram of H2O is released from 138 x 40.37 / (3 x 18) of MgCO3.3H2O

= 103.168 grams of MgCO3.3H2O