5. Periodic Classification of Elements Science class 10 in English Medium ncert book solutions Additional Questions With Solutions

Question 1 : Write the common name of CaO(s).

Answer: Limestone.

Question 2 : Why is sodium hydrogen carbonate a main ingredient of antacids?

Answer: Since sodium hydrogen carbonate is an alkaline substance it neutralizes acids.

Question 3 : In what physical states are the reactants and products represented in a chemical reaction?

Answer: In the form of solid (s), liquid (l), gas (g) and aqueous solution (aq).

Question 4 : What happens when a magnesium ribbon is lit in the presence of air?

Answer: It forms white colored magnesium oxide.

Question 5 : Why is respiration called an exothermic reaction? Give reason.

Answer: The process of respiration which takes place continuously in our cells is a type of exothermic reaction. After breaking down the carbohydrates obtained from food, it is converted into glucose, which together with oxygen in the respiration process gives us energy. Since energy is also released in exothermic reaction, therefore respiration is also called exothermic reaction.

Question 6 : Name the reaction in which two or more reactants combine to form a single product. Write a balanced equation for this reaction.

Answer: Combination reaction.

          C + O₂ - CO₂

Question 7 : Which gas is used in the packing bag to keep the fatty or oily food material for a long time? Why ?

Answer: Oxygen is removed from the bag and made with nitrogen, this eliminates the possibility of oxidation and the substances kept in the bag do not discolor.

Question 8 : What properties do they get from the oxidation of fatty or oily food ingredients?

Answer: They become foul smelling.

Question 9 : Write two important measures to slow down the rate of oxidation of fatty or oily food ingredients.

Answer:

Keeping it in an airtight container speeds up the oxidation.
Removing oxygen from the pouch and containing it with nitrogen eliminates the possibility of oxidation.
Question: Name the reaction in which exchange of ions takes place between the reactants.

Question 10 : What is a chemical reaction called?

Answer: Such processes in which substances with new properties are formed are called chemical reactions.

For example, curd formation from milk, rusting of iron etc.

Question 11 : What are chemical equations called?

Answer: When a chemical reaction is expressed through symbols or formulas, it is called a chemical equation.