Write an equilibrium expression for each chemical equation involving one or more solid or liquid reactants or products.

(a)

(b)

(c)

(d)

Solution 45P :

Step 1:

Here, we have to write the equilibrium expression for each chemical equation. First, let’s see what is an equilibrium expression and then look at the rules for writing equilibrium expression :

An equilibrium expression is an expression that gives the ratio between the products and reactants. It is equal to the concentration of each product raised to its coefficient and multiplied together, divided by the concentration of the product of reactants to the power of their coefficients.

Consider a reaction :

aA + bB cC + dD

Equilibrium expression is written as :

Keq =

Now, let’s see the rules for writing the equilibrium expression :

- The products of the reaction are always written in the numerator.
- The reactants are always written in the denominator.
- Only gases and liquids are included in the equilibrium expression and solids are never included in the equilibrium expression.
- If a reaction contains liquid, then we include it in the expression only if there are multiple liquids. If there is only one liquid, then we will not include it in the expression.

Example : Consider a reaction where water is the only liquid, then the equilibrium expression would not contain water.