Two organic compounds 'X' and 'Y' containing carbon and hydrogen only have vapour densities 13 and 39 respectively. State the molecular formula of 'X' and 'Y' [C = 12, H = 1]

A compound has the following % composition. Zn = 22.65%; S = 11.15%; O = 61.32% and H = 4.88%. It's relative molecular mass is 287 g. Calculate it's molecular formula assuming that all the hydrogen in the compound is present in combination with oxygen as water of crystallization. [Zn = 65, S = 32, O = 16, H = 1]

An organic compound on analysis gave H = 6.48% and O = 51.42%. Determine it's empirical formula if the compound contains 12 atoms of carbon. [C = 12, H = 1, O = 16]

A hydrated salt contains Cu = 25.50%, S = 12.90%, O = 25.60% and the remaining % is water of crystallization. Calculate the empirical formula of the salt. [Cu = 64, S = 32, O = 16, H = 1]