According to Boyle's law, the product of pressure and volume for a fixed mass of gas at constant temperature is: MCQ with Answer and Explanation

Explanation:
Radioactive decay is a first-order process because the rate of decay is proportional to the number of radioactive nuclei present. Half-life is constant, independent of initial amount.

Explanation:
Soap (sodium carboxylate) reacts with Ca²⁺ and Mg²⁺ ions present in hard water to form an insoluble precipitate known as scum. This reduces lathering and wastage of soap. Synthetic detergents do not form scum because their calcium/magnesium salts are soluble.

Explanation:
Mendeleev left gaps and predicted properties of eka-boron (scandium), eka-aluminium (gallium), and eka-silicon (germanium). Germanium was discovered in 1886, its properties matched predictions, confirming the periodic law.