Question

For hydrated copper (II) sulfate calculate the mass percentage of water in your hydrated crystals.

Answer 1

Answer:

56.44 %

Explanation:

The formula of copper(II) sulfate pentahydrate is $CuSO_4\cdot 5H_2O$.

In order to calculate the mass percentage of water in it, we may assume that we have 1 mol of copper(II) sulfate pentahydrate. In general, the mass percentage is a ratio between the mass of a component and the total mass of the compound expressed in percent:

$\omega = \frac{m_c}{m_t}\cdot 100 \%$

Since we're taking 1 mole of a substance here, we may state that the mass percentage of water will be calculating using molar masses instead:

$\omega_{H_2O} = \frac{5M_{H_2O}}{M_{CuSO_4\cdot 5 H_2O}}\cdot 100 \%$

Notice that we take 5 molar masses of water, as 1 mole of copper(II) sulfate pentahydrate contains 5 moles of water molecules, then:

$\omega_{H_2O} = \frac{5\cdot 18.016 g/mol}{159.609 g/mol}\cdot 100 \% = 56.44 \%$