Question

A compound with the formula XOCl3 is synthesized, isolated and purified.

When 3.270 g of this compound are decomposed chemically, a solution of chloride ions is produced.

The chloride ions are precipitated with silver ions and 9.170 g of silver chloride, AgCL, are produced.

What are the identity and molar mass of the element X?

This is likely on my final and my professor did not explain how to solve in class, he just laid it out there and 96% of the class failed the question. Thank you for any help!

Answer 1

clorine precipited as AgCl

molar mass of AgCl = 143.32 gm/mol

molar mass of Cl = 35.453 gm/mol

1 mole of AgCl contain 1 mole of Cl that mean 143.22 gm of AgCl contain 35.453 gm Cl then 9.170 gm AgCl contain 9.170 35.453 / 143.22 = 2.26996 gm of Cl

molar mass of Cl = 35.453 gm/mol then 3 mole Cl = 106.359 gm

molar mass of O = 15.9994 gm/mol

Compound contain 3 Cl and and 1 O

that mean when compound contain 106.359 gm Cl then it contain 15.9994 gm of O

then when compound contain 2.26996 gm of Cl then O contain = 2.26996 15.9994 / 106.359 = 0.341466 gm of O

mass of X = total mass of compound - mass of Cl - mass of O

= 3.270 - 2.26996 - 0.341466

= 0.658574 gm of X

in compound X and O are in equimolar proportion therefore no. of mole of X = no. of mole of O

calculate no. of mole of O

no. of mole = mass O/molar mass of O = 0.341466/15.9994 = 0.0213424253 mole of O

then 0.0213424253 mole of X present in sample

0.0213424253 mole = 0.658574 gm of X then 1 mole of X = 1 0.658574 / 0.0213424253 = 30.9 gm/mole

molar mass of X = 30.9 gm/mole

molar mass of P = 30.97 gm/mole thus X = P

X is phosohorus