Q64 / 180 · AIIMS 2004 · Chemistry

Assertion : Aqueous gold colloidal solution is red in colour. Reason : The colour arises due to scattering of light by colloidal gold particles.

  • Correct answer
    A
    If both assertion and reason are true and reason is the correct explanation of assertion
  • B
    If both assertion and reason are true but reason is not the correct explanation of assertion
  • C
    If assertion is true but reason is false
  • D
    If both assertion and reason are false.

Solution

The colour of colloidal solution depends on the wavelength of light scattered by the dispersed particles. The wavelength of light further depends on the size and nature of the particles. The colour of colloidal solution also changes with the way the observer receives the light. Finest gold sol is red in colour. As size of the particles increases, it becomes purple, then blue and finally golden yellow.

Hence, the correct answer is option: 'A'.

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