Question

Choose the correct statements from the options given in pair.

• A. Alizarin red is a natural dye;
  Manganese dioxide imparts black colour to glasses.
• B. Alizarin red is a synthetic dye;
  Chromium ions impart green colour to glasses.
• C. Indigo blue is a natural dye;
  Cobalt oxide imparts blue colour to glasses.
• D. Indigo blue is a synthetic dye;
  Ferric ions imparts yellow colour to glasses.

Answer 1

The correct option is C Indigo blue is a natural dye;

Cobalt oxide imparts blue colour to glasses.
Alizarin red and indigo blue are natural dyes obtained from plants. Synthetic dyes are manufactured using chemicals.

Following are the colour imparted to glasses when certain transition metals are added:

• Ferric ions gives yellow colour to glasses.
• Chromium/ ferrous ions give green solour to glasses.
• Cobalt oxide gives blue colout to glasses.
• Manganese dioxide imparts purple colour to glasses.