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) We will put the (aq) sign after the element to which water is added.

For example, the precipitation reaction between sodium hydroxide and copper chloride: $2NaOH\left(aq\right)+CuC{l}_2\left(aq\right)⟶2NaCl\left(aq\right)+Cu{\left(OH\right)}_2\left(s\right)\downarrow$

(b) We will show that energy is released as a product of the reaction.

For example, the combustion of carbon: $C\left(s\right)+O_2\left(g\right)\to C{O}_2\left(g\right)+heat$

(c) We will show that energy is consumed by putting the name of the form of energy (eg heat, sunlight, etc.) on the arrow between the reactants and the products.

For example, the formation of nitric oxide: $N_2\left(g\right)+O_2\left(g\right)+heat⟶2NO\left(g\right)$