Question

When water is added to quicklime rise in temperature is observed. This is an example of _____ reaction

Answer 1

Exothermic reactions:

• A chemical reaction in which heat is given out is called an exothermic reaction.
• The heat evolves after breaking the chemical bond between the molecules.
• In an exothermic reaction, the change in enthalpy $\left(\mathrm{\Delta H}\right)$ will be negative.

The reaction of quicklime with water:

• When quicklime$\left(\mathrm{CaO}\right)$ reacts with water$\left({\mathrm{H}}_2\mathrm{O}\right)$, Calcium hydroxide $\left(\mathrm{Ca}{\left(\mathrm{OH}\right)}_2\right)$ is formed along with the liberation of heat. Thus it is considered an Exothermic reaction.
• The chemical reaction can be depicted as:

$\mathrm{CaO}\left(\mathrm{s}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\to \mathrm{Ca}{\left(\mathrm{OH}\right)}_2\left(\mathrm{aq}\right)$
Hence, when water is added to quicklime rise in temperature is observed. This is an example of an exothermic reaction.