Question

A 32.14 gram sample of a hydrate of MnSO4 was heated thoroughly in a porcelain crucible, until its weight remained constant. After heating, 17.51 grams of the dehydrated compound remained. What is the formula of the hydrate?

Answer 1

Answer:

MnSO₄.7H₂O

Explanation:

To solve this question, we need to convert the mass of the dehydrated MnSO₄. The difference between mass of the hydrate and dehydrated compound is the mass of water. With the mass we can find the moles of water and the formula of the hydrate:

Moles MnSO₄ -Molar mass: 151g/mol-:

17.51g * (1mol / 151g) = 0.116 moles

Moles H₂O -Molar mass: 18g/mol-:

32.14g-17.51g = 14.63g * (1mol / 18g) = 0.813 moles

The ratio of moles MnSO₄: Moles H₂O represent the amount of water molecules in the hydrate:

0.813mol / 0.116mol = 7 molecules of water.

The hydrate formula is:

MnSO₄.7H₂O