1. Acid – Base Equilibrium Problem #13

2. Example: Calculate the number of grams of NH 4 Br that have to be dissolved in 1.00L of water at 25 o C to have a solution with a pH of 5.1.

3. The only dissociation that we need to consider is: NH 4 +  NH 3 + H +,

4. Example: Calculate the number of grams of NH 4 Br that have to be dissolved in 1.00L of water at 25 o C to have a solution with a pH of 5.1. The only dissociation that we need to consider is: NH 4 +  NH 3 + H +,

5. Example: Calculate the number of grams of NH 4 Br that have to be dissolved in 1.00L of water at 25 o C to have a solution with a pH of 5.1.

9. The only dissociation that we need to consider is: NH 4 +  NH 3 + H +, if pH = 5.16, then [H + ] = 10 –pH = 10 –5.16 = 6.9  10 –6 M This is also the required value for [NH 3 ], since they are formed in a one-to-one mole ratio. K a = [H + ][NH 3 ]/[NH 4 + ] = 5.6  10 –10 and we arrive at: 5.6  10 –10 = (6.9  10 –6 )(6.9  10 –6 )/[NH 4 + ] [NH 4 + ] = 8.5  10 –2 M 8.5  10 –2 mol/L  97.9 g/mol = 8.3 g NH 4 Br are needed per liter.