Check your answer...do you agree? Great if you do. If you do not check the Solution: below the table to see how the number of molecules of H2SO4 is calculated.

Formula

M , Molar Mass

(g­mol-1)

mass of sample

(g)

n, number of

moles of sample

N, number of atoms,

molecules or formula units

H2SO4

98.0

0.825

0.00842

5.07x 1021 molecules

Solution:

We are to calculate the number of molecules in the sample. How do we know we calculating molecules, rather than atoms or formula units? Since H2SO4 is a covalent compound it exists as molecules at the atomic level. To convert from moles to molecules we need to use Avogadro's number.

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