Question

Iron forms a series of compounds of the type Fe_x(CO)_y. If you heat any of these compounds in air, they decompose to Fe₂O₃ and CO₂ gas. After heating a 0.166g sample of Fe_x(CO)_y, you isolate the CO₂ in a 2.50L flask at 27°C. The pressure of the gas is 33.42mmHg. What is the formula of Fe_x(CO)_y? Show all calculations.

Answer 1

volume of CO2 = 2.50 L

temperature = 27 oC = 300 K

pressure = 33.42 mmHg = 0.04397 atm

P V = n R T

0.04397 x 2.50 = n x 0.0821 x 300

n = 4.463 x 10^-3

moles of CO2 = 4.463 x 10^-3

Fex(CO)y + O2 --------------> x Fe + y CO2

moles of CO = 4.463 x 10^-3

mass of CO = 0.125 g

mass of Fe = 0.0410 g

moles of Fe = 7.34 x 10^-4

ratio :          Fe             CO

            7.34 x 10^-4      4.463 x 10^-3

                    1                     6

Formula = Fe(CO)6