Question

3
.
How will you indicate the following effects in a chemical equation?
(a) Evolution of a gas
(b) Formation of a precipitate
(c) A solution made in water
(d) Exothermic reaction
(e) Endothermic reaction​

Answer 1

(i) For evolution of gas the symbol (g) or sign ↑

(ii) (s) or ↓

(iii) Aqueous represented as (aq)

(iv) Exothermic reaction convention = ΔH = - ve

(v) Endothermic reactions convention = ΔH = + ve

Answer 2

1. arrow mark upward in direction Ca + 2HCl -----------> CaCl2 + H2 (↑) (arrow mark upward in direction)

2. arrow mark downward in direction Pb(NO3)2 + 2KI gives 2KNO3 + PbI2 (↓) (arrow mark downward in direction )

3. (aq) aq stands for aqueous sol.

NaOH --------------------> Na+ (aq) + OH-(aq)

4.An exothermic reaction is indicated by writing "+Heat" or "+Heat energy" or "+Energy" on the products side of an equation.

5.An endothermic reaction is indicated by writing "+Heat" or "+Heat energy" or "+Energy" on the reactants side of an equation.

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