Mole Fraction

• The mole fraction is a unit of concentration, defined to be equal to the number of moles of a component divided by the total number of moles of a solution
• The mole fraction is determined for all reactants in a mixture of gases
• g. to find the mole fraction of A (Xa): Partial pressure

• Partial pressure it the pressure exerted by the single gas if it were isolated
• The total pressure is the combined total of all the partial pressures
• To determine the partial pressure for one gas, multiply the mole fraction by the total pressure
• g. to find the partial pressure of A (PA):
• Units for partial pressure Pascals or atmospheres

PA = Mole Fraction of A  x Total Pressure

PA = Xa  x   P

Kp in homogeneous gaseous equilibria

• Homogeneous Equilibria refers to all involved reactants are in the same phase
• For Kp to function, everything must be a gas • Kp will always be a constant except for a change in temperature Kp in heterogeneous equilibria

• Heterogeneous equilibrium will involve gases in contact with solids
• As Kp functions only with a gas, the solid is not included