Concentration of Ammonia in a Solution

How do we determine the concentration of ammonia in a solution?

A solution is prepared by dissolving 0.20 mol of acetic acid and 0.20 mol of ammonium chloride in enough water to make 1.0 L of solution. Find the concentration of ammonia in the solution.

Determination of Ammonia Concentration in the Solution

The concentration of ammonia in the solution is 0.20 M.

Let's understand how we determine the concentration of ammonia in the solution. In this case, a solution is prepared by dissolving 0.20 mol of acetic acid and 0.20 mol of ammonium chloride in enough water to make 1.0 L of solution. The goal is to find the concentration of ammonia in the resulting solution.

To determine the concentration of ammonia, we need to consider the chemical reactions that occur when ammonium chloride dissociates in water and when ammonia reacts with water.

When ammonium chloride dissociates in water, it forms ammonium ions (NH4+) and chloride ions (Cl-). This dissociation equation is represented as follows:

NH4Cl (s) → NH4+ (aq) + Cl- (aq)

Ammonia (NH3) is a weak base and reacts with water to form ammonium ions (NH4+) and hydroxide ions (OH-). The reaction equation is:

NH3 (aq) + H2O (l) → NH4+ (aq) + OH- (aq)

From the given data, we know that 0.20 mol of ammonium chloride was added to the solution. This means that there are also 0.20 mol of ammonium ions present in the solution.

Because one mole of ammonium chloride dissociates to form one mole of ammonium ion, we can assume that there are 0.20 mol of ammonia in the solution as well. Therefore, the total moles of ammonia in the solution is also 0.20 mol.

The total volume of the solution is 1.0 L. Therefore, the concentration of ammonia in the solution can be calculated as:

[ NH3 ] = 0.20 mol / 1.0 L = 0.20 M

Hence, the concentration of ammonia in the solution is 0.20 M.

By following the chemical reactions and stoichiometry, we can accurately determine the concentration of ammonia in a solution.