Some of the questions and their solutions from NCERT Solutions for Class 10: Chemical Reactions and Equations, are as follows:

Q. Why should a magnesium ribbon be cleaned before burning in air?

Sol. Magnesium is an extremely reactive metal. In the presence of oxygen, it forms a layer of magnesium oxide on its surface. This layer is quite stable and doesn’t allow further reaction of magnesium with oxygen. Thus, it is necessary to clean magnesium, rubber so that the underlying metal can be available for reaction.

Q. Why is the amount of gas collected in one of the test tubes in Activity 1.7 double of the amount collected in the other’ Name this gas.

Sol. Water contains hydrogen and oxygen in the ratio of 2:1. Hence, the amount of hydrogen and oxygen produced during electrolysis of water is in a 2:1 ratio. During electrolysis, since hydrogen goes to one test tube and oxygen goes to another, the amount of gas collected in one of the test tubes is double of the amount collected in the other.

Q. What is a balanced chemical equation? Why should chemical equations be balanced?

Sol. Balanced chemical equation: - A reaction which has an equal number of atoms of all the elements on both sides of the chemical equation is called a balanced chemical equation.

As per the law of conservation of mass, mass can neither be created nor destroyed. Hence, in a chemical reaction, the total mass of reactants should be equal to the total mass of the products. Thus, the total number of atoms of each element should be equal on both sides of a chemical equation.

Q. Oil and fat containing food items are flushed with nitrogen. Why?

Sol. Nitrogen is an inert gas and does not easily react with these substances whereas oxygen reacts with food substances and makes them rancid. Thus, bags used in packing food items are flushed with nitrogen gas to remove oxygen inside the pack. When oxygen is not present inside the pack, rancidity of oil and fat containing food items is avoided.