Question

What is the importance of a chemical equation:
$(i)$ Determine the effect of temperature and pressure
$(ii)$ Physical states of reactants and products
$(iii)$ Relative masses of reactants and products
$(iv)$ Determine the atomic number of substances

Answer 1

Chemical equation is the representation of the chemical reaction. The chemical equation contains reactants and products. Also they contain chemical reagents and catalysts. Chemical equation represents the energy released or gained during conversion of reactants to products.

Complete answer:
The chemical equation gives us a brief description of the chemical reaction. We can also say that a chemical equation is a symbolic representation of the molecules which take part in the chemical reactant. Also chemical equations give us the knowledge of the amount of reactant used and the amount of products formed during the chemical reaction. The chemical transformation can be depicted by using the chemical reactions. The amount of heat energy evolved or absorbed during a reaction is depicted with the help of the chemical equation. The reactions take place at a constant temperature and constant pressure. But when we change the temperature and the pressure of the reaction, the effect caused by this change is depicted with the help of chemical equations only. Chemical reactions do not tell us about the physical states of the elements. It tells us about the present state of the atoms or ions. Also with the help of an equation we cannot determine the atomic number of the molecules which take part in the chemical reaction.
Therefore we can say that with the help of chemical equations we can determine the effect of temperature and pressure on the chemical reaction.
Thus the correct option is $(i)$ .

Note:
Chemical reactions only tell us about the transformation of the molecule after reacting with other molecules. Thus the physical state of a molecule cannot be predicted with the help of chemical equations. The relative masses cannot be determined with the help of a chemical equation.