Question

Examples of slow reaction are:
(A) Rusting of iron
(B) Weathering of rocks
(C) Neutralization of sodium hydroxide by hydrochloric acid
(D) Formation of coal

Answer 1

Hint: To determine if a reaction is slow or fast we need to look at the rate of reaction. The rate of reaction depends on four main criteria: the physical state of the reactants, and surface area, temperature, and the presence of a catalyst.

Complete step by step answer:
Let us first understand each of the reactions given to us in detail.

Rusting of iron: This refers to the formation of iron oxides on the surface of Iron. It occurs primarily when iron objects are exposed to a lot of moisture in presence of oxygen. Rust is characterized by formation of res, flaky substance that easily crumbles to powder. However the reaction is not instantaneous but takes a sufficiently long period of time instead.

Weathering of rocks: This refers to disintegration of rocks due to natural reasons such as wind, water and temperature. It transforms the original material into a substance with a different composition and different physical characteristics. This too takes a really long time.

Neutralization of Sodium hydroxide by Hydrochloric acid: This is a neutralization reaction forming salt and water. It occurs through formation of ions and is instantaneous.

Formation of coal: This process takes over millions of years. Dead plant and animal matter decays into peats which finally get converted to coal due to extreme heat and pressure sustained.

Hence, the correct answers are Options A, B and D.

Note: After solving this question we can conclude that most naturally occurring reactions are slow. But certain reactions which are conducted in the laboratories often take too much time. In these cases, we use catalysts to speed them up.