A solution turns blue litmus red. The solution is: MCQ with Answer and Explanation

Explanation:
Rate ∝ 1/√M. Molar masses: H₂=2, CH₄=16, NH₃=17, CO₂=44. CO₂ has highest mass, diffuses slowest.

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:
The strong nuclear force is the attractive force that binds protons and neutrons (nucleons) together in the nucleus, overcoming the electrostatic repulsion between protons. It is short-range and charge-independent. Electrostatic repulsion would otherwise blow the nucleus apart. Gravitational force is negligible at this scale. Van der Waals forces operate between molecules.