Core practical 9 - determining Ka of a weak acid

Use the pH of your solution to calculate [H+ ].

Depends on your findings but the pH should be 4.77; so [H⁺] = 1.7 × 10⁻⁵moldm⁻³.

Calculate a value of Ka for ethanoic acid.

1.7 × 10⁻⁵moldm⁻³

What are some of the sources of uncertainty in this experiment? What can you do to overcome them?

Sources of uncertainty include inaccuracy of burette readings, and difficulty identifying the exact end point. Read glassware from the bottom of the meniscus; use a white tile so you can see the colour change clearly.

Safety

• Sodium hydroxide in an irritant

• Eye protection

• Lab coat