You are Here: Home

# Quick question about Molecular formula watch

1. 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?!
2. 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:
3. (Original post by 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!

### Related university courses

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: January 27, 2010
Today on TSR

### Results day under a month away

How are you feeling?