It is useful to know the colour of some compounds commonly reacted with acids to work out if a colour change has occurred.

The acid and conjugate base each have different colors and as the equilibrium shifts from one direction to the other, the color of the indicator changes. As an example, the equilibrium of a weak acid ...

In this reaction we are going to react an acid with an alkali and measure the temperature change during the reaction. The acid will react to produce a salt and water – no gas is produced.