Which of the following causes ozone depletion? MCQ with Answer and Explanation

Explanation:
Down Group 1 (Li → Fr), atomic radius increases due to addition of electron shells. Ionization energy and electronegativity decrease. Reactivity with water increases because the outer electron is more easily lost. Density generally increases, melting/boiling points decrease. Cesium and francium are most reactive. The increase in radius is due to principal quantum number increase.

Explanation:
Boyle's law: P₁V₁ = P₂V₂. So P₂ = P₁(V₁/V₂) = P₁(10/20) = P₁/2. Pressure is halved. If volume doubles, pressure halves, assuming constant temperature and amount. This is an inverse relationship.

Explanation:
A positive catalyst increases reaction rate by lowering activation energy. Decreasing temperature generally slows reactions. Decreasing concentration reduces collision frequency, lowering rate. Larger pieces have less surface area, slower reaction. Other rate-increasing factors: increasing temperature, increasing pressure (for gases), using finely powdered solids, and light for photochemical reactions.