# What's the molecular formula of a compound with 52% C, 3.15% H, 44.4% Cl if the formula weight is 320g/mol?

Assuming 100g of the substance, giving 52g C, 3.15g H, and 44.4g Cl. What is the molecular formula?

Thanks.

If possible, please provide the solution. Thank you!

### 2 Answers

- 1 decade agoFavorite Answer
OK....you've done the first step, by looking at 100g

Now, the second step is to convert each element to no of moles, by dividing mass by molar mass:

C: 52 / 12 = 4.33 mol

H: 3.15 / 1 = 3.15 mol

Cl: 44.4 / 35.5 = 1.25 mol

Now, divide all mol by the smallest quantity, which in this case is that of Cl (1.25).

C: 4.33 / 1.25 = 3.464 approx equal to 3.5

H: 3.15 / 1.25 = 2.52 approx equal to 2.5

Cl: 1.25 / 1.25 = 1

However, we cannot have fractions in the formula, so multiply everything by 2:

C: 3.5*2 = 7

H: 2.5*2 = 5

Cl: 1*2 = 2

So the empirical formula is C7H5Cl2

The molar mass of the empirical formula is 160

But the formula mass is 320

So the number of units of the empirical formula in the molecular formula is (320/160) = 2

So your molecular formula is (C7H5Cl2)2 = C14H10Cl4

I hope it's right.

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- sahsjingLv 71 decade ago
First, you need to find molar ratio.

C: 320(.52/12) = 14 mol

H: 320(.0315/1) = 10 mol

Cl: 320(.444/35.45) = 4 mol

Therefore, the molecular formula is C14H10Cl4

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