Acompound is composed of 85.64% carbon and 14.36% hydrogen. the compound has a formula mass of 42.08 grams. what is the molecular formula?

Explanation:

1) Assume 100 g of substace:

2) Convert the masses in grams to number of moles

Calculations:

3) State the ratio of moles.

Divide the number of moles of each element by the least number of moles:

4) Set the empirical formula:

5) Calculate the mass of one mol of the empirical formula:

6) Calculate how many times the mass of the empirical formula is contained in the mass of the molecular formula:

7) Set the molecular formula:

Multiply each subscript of the empirical formula by the previos ratio: 3

Conclusion: the molecular formula is C₃H₆

C₃H₆

Explanation:

1. for the first question, we must find the mass of the anhydrous salt, mgso₄. the molar mass for mgso₄·7h₂o is 246.47 g/mol, while that of mgso₄ is 120.37 g/mol.7.834 g mgso₄·7h₂o * 1 mol mgso₄·7h₂o/246.47 g * 1 mol mgso₄/1 mol mgso₄·7h₂o * 20.37 g mgso₄/mol = 0.647 g mgso₄

2. mass of water = mass of sample - mass of anhydrous salemass of water = 7.834 - 0.647 = 7.19 gpercent water in hydrate = 7.19/7.834 * 100 = 91.74%