Chemical Reactions and Equations — Important Questions

Change in color, Evolution of gas, Change in temperature, Change in state

Chemical reactions can be identified by observing changes in color, evolution of gas, temperature changes, and changes in state. These indicate that the chemical composition has changed. A mere change in shape without other indicators is usually a physical change.

2FeSO₄ → Fe₂O₃ + SO₂ + SO₃, CaCO₃ → CaO + CO₂, 2H₂O → 2H₂ + O₂

Decomposition reactions involve a single reactant breaking down into two or more products. The first three options show this pattern. The last two are combination and displacement reactions respectively.

True

Respiration is indeed an exothermic reaction. During respiration, glucose combines with oxygen to produce carbon dioxide, water, and energy. The energy released is used by our body for various life processes.

(s) for solid, (l) for liquid, (g) for gas, (aq) for aqueous solution

The standard symbols for physical states are (s) for solid, (l) for liquid, (g) for gas, and (aq) for aqueous solution (dissolved in water). There is no standard symbol (p) for powder.