Important questions based on NCERT syllabus for Chapter 1 - Chemical Reactions and Equations:
Question-1: How can you help your mother in keeping the fried items so that they do not develop a foul smell and their shelf life is increased?
Solution: 1. Since we cannot pack the fried objects in the atmosphere of nitrogen at home, we can increase their shelf life by keeping them in airtight containers.
2. In this way they do not come in contact with oxygen.Their shelf life can further be increased by refrigerating at low temperature.
Question-2: What is exothermic and an endothermic reaction. Amongst the following reactions, identify the exothermic reaction and the endothermic reaction:
- Heating coal in air to form carbon dioxide.
- Heating limestone in lime kiln to form quick lime.
Solution: 1. Exothermic reactions are those reactions in which heat is evolved. Endothermic reactions are those which involve absorption of heat.
2. Heating coal in air to form carbon dioxide is an exothermic reaction.
3. Heating limestone in a lime kiln to form quick lime is an endothermic reaction.
Question-3: What factors influence the rate of chemical reaction?
Solution:Following are the factors that can influence the rate of reaction:
- Nature of Reactants. E.g. Mg reacts faster in HCl than in acetic acid. Concentration of reactants
- Surface Area of reactants. E.g. Powdered
CaCO3 reacts quicker than marble chips.
- Temperature and Catalyst