a 5.49g sample of iron(iii) chloride hydrate was found to contain 2.20g of water. what is the complete formula of the hydrate?

Question

aaronq · Answer

so you have 2.2g of water.. 2.2g/18g/mol = 0.1222 moles of H2O
and you have 5.49-2.2= 3.29 g iron(III)chloride  

since you know Fe is in oxidation state of 3+, the formula is FeCl3  
ie. Fe +3  and  Cl - so you need 3 Cl's to balance the charge..

now to find the moles of FeCl3 = 3.29g/162.19g/mol  =0.0203

divide the larger by the smaller

0.12222/0.0203 = 6  so the ratio of FeCl3 : H2O is 1:6

FeCl3(H2O)6