A sample of a compound contains 30.0 g calcium and 5.05 g hydrogen. its molar mass is 78.12 g/mole. what is the compound's molecular formula?

There is a fault in the question. The ratios do not add up as seen in the calculations below.

Moles of Ca 30/40.1 = 0.748 (3sf)

Moles of H 5.05/1 = 5.05

molar ratios (divide both sides by 0.748)

Ca:H

1: 6.75 = 2:13.5 = 4:27

Therefore Ca4H27.

This gives a molar mass of 160.4+27 = 187.4. Either the mass of hydrogen or the mass of calcium is wrong.