Question

How will you provide the following information in a chemical equation?

Evolution of heat

Answer 1

1. Chemical Equation: A chemical equation is a shorthand method to describe the reaction taking place in terms of symbols and formulae of substances involved in the reaction.
2. Endothermic reactions: Certain reactions absorb heat to proceed. Example- Photosynthesis

$$\begin{gathered} 6{\mathrm{CO}}_2\left(\mathrm{g}\right)+6{\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right)+\mathrm{Heat}\to {\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6\left(\mathrm{s}\right)+6{\mathrm{O}}_2\left(\mathrm{g}\right) \\ \mathrm{Carbon}\mathrm{water}\mathrm{Glucose}\mathrm{Oxygen} \\ \mathrm{dioxide} \end{gathered}$$

3. Exothermic reactions: Certain reactions evolve heat during the reaction.

Example-$$\begin{gathered} \mathrm{C}\left(\mathrm{s}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)\to {\mathrm{CO}}_2\left(\mathrm{g}\right)+\mathrm{Heat} \\ \mathrm{Carbon}\mathrm{Oxygen}\mathrm{Carbon} \\ \mathrm{dioxide} \end{gathered}$$

4. Representation of heat involved in a chemical reaction:

• The word ‘Heat’ is used to show the heat involved during a reaction.
• For an exothermic reaction, '+ Heat' is written on the product side, and for the endothermic reaction, '+Heat' is written on the reactant side, or '- Heat' is written on the product side.

5. Hence, the evolution of heat in a chemical equation is provided by writing ‘ +Heat’ on the product side.