Chemical Equilibrium

Generally for the reaction:

we have:

where is the equilibrium concentration in

Determine for the reaction given by the balanced equation below:

if the concentrations at equilibrium are:

solution

Generally for the reaction:

we have:

where is the partial pressure at equilibriium

For the reaction:

we can use Ideal Gas Law to derive:

where:

• is the universal gas constant. If pressure is in bar, then the value is

Consider the reaction:

with at . Calculate .

solution

When writing expressions for the equilibrium constant, pure liquids and solids are not included

Consider the reaction:

Since is a solid, and its density/molar mass is constant, we can write:

For the general equation:

we have

where:

• For pure liquids and solids,
• For aqueous components, , (what???)
• For gaseous components, ,
• For ideal gas mixtures and ideal solutions,

The reaction of nitrogen and hydrogen to produce ammonia is shown below:

1.0 mol of and 3.0 mol of are introduced into a rigid 30 L vessel that is held at a constant
temperature of 800 K. The total pressure at equilibrium is 8.1 bar. Determine .

solution
To find the partial pressures of the reactants, use Ideal Gas Law:

ICE table:

Note the partial pressure of is , not .

A mixture of and at the stoichiometric ratio (according to the reaction below), is allowed to come at equilibrium at a constant temperature ant total pressure of .

with .

At equilibrium, 40% of the is found to have converted to . What is the temperature ?

solution

Idea: assume of . Use ICE table to find moles of each, then find using . Finally, use ideal gas law to find .

Now use ideal gas law to find :