Question

When acid react with phenol red colour changes from?

Answer 1

Carbon dioxide reacts with water to form carbonic acid. Eventually it will produce enough acid to cause the color of the indicator to change. Phenol red is red at pH 8.5 and turnsyellow at pH 6.8.

Answer 2

It is a weak acid with pKa = 8.00 at 20 °C (68 °F). A solution of phenol red is used as a pH indicator, often in cell culture. Its color exhibits a gradual transition from yellow (λmax = 443 nm) to red (λmax = 570 nm) over the pH range 6.8 to 8.2. Above pH 8.2, phenol red turns a bright pink (fuchsia) color.

Chemical formula: C19H14O5S

Molar mass: 354.38 g·mol−1