A compound with the empirical formula ch2 has a molar mass of 70 g/mol. what is the molecular formula for this compound?

The empirical formula, C H2, has a relative molecular mass of

1 * (12.01) + 2 * (1.01) = 14.04

This means that the empirical formula must be multiplied by a factor to bring up its molecular weight to 70. This factor can be calculated as the ratio of the relative masses of the molecular and empirical formulas

7014.04 = 4.98≈5

Remember that subscripts in molecular formulas must be in whole numbers, hence the rounding-off. Finally, the molecular formula is

C 1*5 H 2*5 = C5 H 10