Quick question about Molecular formula

0.167g sample of iron reacts with a stream of dry chlorine to form 0.487g of solid X. The molar mass of solid X was determined to be 324.6g/mol

Calculate the molecular formula of X.

RAM of iron - 55.8. RAM of chlorine 35.5.
0.487-0.167=0.320grams of chlorine

So 0.167/55.8 = 0.00299

0.32/35.5 = 0.009014

Ratio 0.00299:0.009014

is 1:3 So empirical formula is FeCl3

Why is the molecular formula Fe2Cl6?!

Reply 1

Kyri

15

The molecular mass of FeCl3 is 162.3 g/mol so that can't be solid X. Multiplying everything by 2 to get Fe2Cl6, however, gives you 324.6 g/mol which you are told is the correct molar mass of sold X. If it's the structure of Fe2Cl6 you're concerned about, I guess it would be something similar to the Al2Cl6 dimer, like this:

Reply 2

Clarity Incognito

OP

11

Kyri

The molecular mass of FeCl3 is 162.3 g/mol so that can't be solid X. Multiplying everything by 2 to get Fe2Cl6, however, gives you 324.6 g/mol which you are told is the correct molar mass of sold X. If it's the structure of Fe2Cl6 you're concerned about, I guess it would be something similar to the Al2Cl6 dimer, like this:

Thank you Very much!

Quick question about Molecular formula

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