According to Graham's law, the rate of diffusion of a gas is inversely proportional to the square root of its: MCQ with Answer and Explanation

Explanation:
Ethanol, commonly known as ethyl alcohol, has the chemical formula C₂H₅OH. Methanol is CH₃OH. Acetic acid (ethanoic acid) is CH₃COOH, and propionic acid is C₂H₅COOH. Ethanol is widely used as a solvent, in alcoholic beverages, and as a biofuel.

Explanation:
The half-life is the time required for half of the radioactive atoms to decay. After 10 years (1 half-life), 1/2 remains. After 20 years (2 half-lives), 1/4 remains. After 30 years (3 half-lives), the fraction remaining is (1/2)^3 = 1/8. Thus, one-eighth of the original sample will remain.

Explanation:
In electrolytic refining of copper, impure copper is used as the anode, a thin sheet of pure copper as the cathode, and CuSO₄ acidified with H₂SO₄ as electrolyte. On passing current, copper dissolves from the anode and pure copper deposits on the cathode. Impurities like gold, silver fall as anode mud. This yields 99.99% pure copper. Similar process for other metals.