Pressure Questions?

Question

Calculate the mass of Iron(III) oxide which would be reduced by 3.5kL of carbon monoxide at 1500.0(deg C) and 102.0 kPa pressure. The equation is

Fe2O3 + 3CO ---> 2Fe + 3CO2

Answer 1

This problem uses stoichiometry and the universal gas law.

The law states PV = nrT and as pressure, volume and temperature are given, n = PV/rT . This will give the number of moles (or "units") of CO used in the reaction. Be careful to convert P, V and T into the same terms expressed in the universal gas constant "r". In this example, the gas constant will need to be expressed in terms of C, kPa and Liters.

Stoichiometry states that 1 unit of Fe2O3 and 3 units of CO will yield 2 units of Fe. Therefore, each unit of CO will reduce one third unit of Fe2O3 to yield two thirds units of Fe.

To solve the problem, calculate the number of moles of CO, and the mass of iron needed will be one third this number of moles. The yield will be two thirds.

NOTE: the equation PV = nrT is only an approximation. It assumes there are no interactions between the gas particles. This is generally true of gasses at very low pressure and high temperature. As more particles are introduced into the system, interactions increase and the equation can not be reliably used.

Answer 2

Use the ideal gas law (PV=nRT) to calculate the number of moles of CO (n). Be sure that you are consistent with your units for pressure, temperature (must be in K) and the gas constant.

The number of moles of Fe2O3 would be 1/3 the moles of CO. Finally, use the molar mass of Fe2O3 to convert that number of moles to a mass.

Answer 3

here the process:
use ideal gas eqn to find mols of CO
PV=nRT
102000Pa*(1atm/101325Pa)=1.006662...
1.00662atm(3500L)=n(0.08206)(1500+273)
n=24.22 mol CO

now use mol ratio
24.22mol CO (1mol Fe2O3/3mol CO) (159.70g Fe2O3/mol Fe2O3) = 1.3 x10^3 g Fe2O3

double check my rounding error