Question

What is the percent by mass of water in MgSO4 • 7H2O? A. 51.1% B. 195% C. 56.0% D. 21.0%

Answer 1

Answer : The correct option is, (A) 51.1%

Explanation :

Mass percent : It is defined as the mass of the given component present in the total mass of the compound.

Formula used :

`\text{Mass} \%H_2O=\frac{\text{Mass of }H_2O}{\text{Mass of }MgSO_4.7H_2O}* 100`

First we have to calculate the mass of
`H_2O` and
`MgSO_4.7H_2O`.

Mass of
`H_2O` = 18 g/mole

Mass of
`7H_2O` = 7 × 18 g/mole = 126 g/mole

Mass of
`MgSO_4.7H_2O` = 246.47 g/mole

Now put all the given values in the above formula, we get the mass percent of
`H_2O` in
`MgSO_4.7H_2O`.

`\text{Mass} \%H_2O=(126g/mole)/(246.47g/mole)* 100=51.1`

Therefore, the mass percent of
`H_2O` in
`MgSO_4.7H_2O` is, 51.1%