Exams › JEE Main › Chemistry

Given below are two statements: one is labelled as Assertion A and other is labelled as Reason R. Assertion A : Finest gold is red in colour, as the size of the particles increases, it appears purple then blue and finally gold. Reason R : The colour of colloidal solution depends on the wavelength of light scattered by the dispersed particles. In the light of the above statements, choose the most appropriate answer from the options given below.

1. Both A and R are true and R is the correct explanation of A
2. Both A and R are true but R is NOT the correct explanation of A
3. A is true but R is false
4. A is false but R is true

Correct answer: A is true but R is false

Solution

Assertion A correctly describes the color changes of gold nanoparticles, which can appear red, purple, and blue depending on their size. However, Reason R is inaccurate because it does not apply to the specific case of gold, as the color of colloidal gold is not solely determined by the wavelength of light scattered by particles, but also by their size and shape.

Related JEE Main Chemistry questions

• At constant temperature, the Freundlich adsorption relation for a gas adsorbed on a solid can be written in terms of the amount adsorbed per unit mass of adsorbent as:
• What is the typical size range of colloidal particles?
• Which of the following is an example of an irreversible colloid when water acts as the dispersion medium?
• Which of the following forms cationic micelles when its concentration exceeds a certain limit?
• In a micelle, how are the polar and non-polar regions arranged?
• What is responsible for Brownian motion?

⚔️ Practice JEE Main Chemistry free + battle 1v1 →