# What is the Relative molecular mass if ZnSO4.7H2O?

What is the Relative molecular mass if ZnSO4.7H2O? Does the ‘.’ mean add, or multiply?

• The dot between the compound and the hydrate (7H20) just indicates that it is a hydrated crystal. So, just add accordingly. Your answer should be about 287.56 g/mol.

• To consider the masses of molecules measured in grams, for example, would be to deal inconveniently with extremely small numbers. Rather, the mass of a molecule is compared with that of an atom of carbon-12. The relative atomic mass of carbon-12 is taken to be 12. Relative masses have no units because they have cancelled in their calculation. A relative molecular mass can be calculated easily by adding together the relative atomic masses of the constituent atoms. For example, ethanol, CH3CH2OH, has a Mr of 46.

• Molar Mass Of Znso4

• The ‘.’ is normally placed in the centre of the line as in ‘ ∙ ‘

ZnSO4∙7H2O. meaning the hydrate molecule contains 7 molecules of water of crystallisation.

Simply adding all the atomic masses of the elements, will give the Molecular mass of the hydrate.

(As a matter of interest..If you take the mol.mass of the ZnSO4∙7H2O and then divide the mol.mass of the 7H2O by the total mol. mass and multiply this by 100%, you’ll find the Percent of water in the hydrate…as follows..

ZnSO4 Mol mass = 65 + 32 + (4 x 16) = 145g/mol.

7H2O mol mass = (7 x 2 x 1) + (7 x 16) = 126g/mol.

Total = 271g/mol.

126g/mol / 271g/mol x 100% = 46.5% water in the hydrate.