Question

Explain the following by giving examples:

Importance of pH in daily life
Exothermic chemical reactions

Hint:

In exothermic reactions, energy is released to the surroundings, which often causes the temperature to rise.

Answer 1

(i) Importance of pH in Daily Life:
pH is a measure of the acidity or basicity of a solution. The pH scale ranges from 0 to 14, where a pH of 7 is neutral, values less than 7 are acidic, and values greater than 7 are basic or alkaline. The importance of pH in daily life is significant, as it affects various biological and chemical processes.
Examples of pH in Daily Life:
- In the Human Body: The pH of blood is maintained around 7.4, which is slightly basic. Any significant deviation from this pH can cause health problems. For example, a lower pH (acidic condition) can lead to acidosis, and a higher pH (basic condition) can lead to alkalosis.
- In Agriculture: Soil pH affects plant growth. Most plants prefer a soil pH between 6 and 7. Soils that are too acidic or too alkaline may hinder plant nutrient absorption.
- In Cleaning Products: Many cleaning agents are either acidic or basic. For example, vinegar (which contains acetic acid) is commonly used to clean surfaces, while baking soda (which is basic) is used to remove stains and odors.
(ii) Exothermic Chemical Reactions:
An exothermic reaction is a chemical reaction that releases energy, usually in the form of heat or light, to the surroundings. These reactions occur when the energy released during the formation of products is greater than the energy required to break the bonds in the reactants.
Examples of Exothermic Reactions:
- Combustion of Fuels: When fuels like wood, coal, or natural gas burn, they undergo exothermic combustion reactions, releasing heat and light. For example, burning methane (\( \text{CH}_4 \)) with oxygen releases a large amount of energy: \[ \text{CH}_4 + 2\text{O}_2 \rightarrow \text{CO}_2 + 2\text{H}_2\text{O} + \text{Energy} \]
- Respiration: In living organisms, respiration is an exothermic process. Glucose combines with oxygen to form carbon dioxide, water, and energy: \[ \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \rightarrow 6\text{CO}_2 + 6\text{H}_2\text{O} + \text{Energy} \] The energy released is used by cells for various functions.
- Dissolving Calcium Oxide in Water: When calcium oxide (\( \text{CaO} \)) is added to water, it reacts exothermically to produce calcium hydroxide (\( \text{Ca(OH)}_2 \)) and heat: \[ \text{CaO} + \text{H}_2\text{O} \rightarrow \text{Ca(OH)}_2 + \text{Heat} \]