Equilibria (A Level)

You will be able to

• Calculate the pH of a buffer solution from Ka and the amounts of weak acid and conjugate base.
• Explain, using equations, how a buffer solution controls pH when a little acid or alkali is added.
• Deduce when a buffer stops working, and how to make a buffer of a required pH.

You will be able to

• Write the expression for Ksp, derive its units and calculate a solubility from Ksp.
• Predict whether a precipitate forms by comparing the ionic product with Ksp, allowing for dilution on mixing.
• Explain and calculate the effect of a common ion on the solubility of a sparingly soluble salt.

You will be able to

• State what is meant by the partition coefficient and calculate Kpc from the concentrations in the two solvents.
• Calculate the mass of solute extracted by one or by successive portions of solvent.
• Explain how the polarity of the solute and of the two solvents affects the value of Kpc.