The time taken for a radioactive substance to reduce to half its initial amount is: MCQ with Answer and Explanation

Explanation:
Magnesium reacts with hot water or steam to form MgO/Mg(OH)₂ and H₂, but very slowly with cold water (thin layer of insoluble hydroxide inhibits reaction). Sodium, potassium, and calcium react vigorously with cold water. Aluminium, zinc, iron react with steam but not cold water. Reactivity with water follows the series: K, Na, Ca (cold water); Mg, Al, Zn, Fe (steam).

Explanation:
Chlorofluorocarbons (CFCs), once widely used as refrigerants and propellants, are the primary culprits behind ozone depletion. When CFCs reach the stratosphere, UV radiation breaks them down, releasing chlorine atoms. A single chlorine atom can catalytically destroy thousands of ozone (O3) molecules.

Explanation:
In electroplating, the electrolyte must contain the ions of the metal to be deposited. To plate silver, a solution of a silver salt, such as silver nitrate (AgNO₃) or silver cyanide, is used. The anode is pure silver, and the cathode is the copper spoon to be plated.