Question

What are the ways by which a chemical equation can be made more informative?

Answer 1

A chemical equation can be more informative by using the following ways:

• The physical state of reactants and products can be indicated by putting (s) for solid, (l) for liquid, (g) for gas, and (aq) for aqueous state. For example,

$Zn\left(s\right)+H_{2}S{O}_4(aq.)\to ZnS{O}_4(aq.)+H_2\left(g\right)$

• Evolution or absorption of heat during the reaction can be denoted by adding or subtracting a heat term on the product side. For example,

$C\left(s\right)+O_2\left(g\right)\to C{O}_2\left(g\right)+\text{Heat}$

• Temperature, pressure, and catalyst can be indicated above the arrow $(\to )$ separating the reactants and products.

$2KCl{O}_3\left(s\right)\underset{Mn{O}_2}{\overset{\Delta }{\to }}2KCl\left(s\right)+3O_2\left(g\right)$

• Concentrations of reactants and products are indicated by adding the words (dil.) for dilute and (conc.) for concentrated before their formulae.
• By the sign $\to$ or $\rightleftharpoons$ information about irreversible and reversible reactions can be obtained.
• Upward arrow $(\uparrow )$ indicates a gas is evolved and downward arrow $(\downarrow )$ indicates a precipitate formed. A sign $\left(\Delta \right)$ that heat is evolved or absorbed.