Question

How will you indicate the following effects in a chemical equation?
(a) A solution made in water
(b) Exothermic reaction
(c) Endothermic reaction

Answer 1

(a) A solution made in water is indicated by writing (aq) after its formula in a chemical equation.
Example: 6CO₂ (g) + 6H₂O (l) $\underset{\mathrm{chlorophyll}}{\overset{\mathrm{sunlight}}{\to }}$ C₆H₁₂O₆ (aq) + 6O₂ (g)

(b) Exothermic reaction is indicated by writing “heat” or “heat energy” or “energy” on the products’ side of a chemical reaction.
Example: CH₄ + 2O₂ → CO₂ + 2H₂O + Heat

(c) Endothermic reaction is indicated by writing “heat” or “heat energy” or “energy” on the reactants’ side of a chemical reaction.
Example: N₂ + O₂ + Heat → 2NO