Chemical Reactions and Chemical Equations

Chapter 1: Chemical Reactions and Chemical Equations from Class 10 NCERT.

Intext Questions:

Page 10:

1. Question:
   What do you understand by a chemical reaction?

   Answer:
   A chemical reaction is a process in which reactants are converted into products through the breaking and forming of chemical bonds, resulting in a change in the composition and properties of the substances involved.

Page 12:

2. Question:
   Write the equation for the reaction between sodium and water.

   Answer:
   The equation for the reaction between sodium and water is:

   2Na + 2H_2O \rightarrow 2NaOH + H_2

3. Question:
   What do you observe when zinc is added to dilute hydrochloric acid?

   Answer:
   When zinc is added to dilute hydrochloric acid, hydrogen gas is released, and a solution of zinc chloride is formed.

Page 13:

4. Question:
   Define a chemical equation. Why is it important to balance chemical equations?

   Answer:
   A chemical equation represents a chemical reaction using symbols and formulas. Balancing chemical equations is important because it follows the law of conservation of mass, which states that mass is neither created nor destroyed in a chemical reaction.

Exercise Questions:

1.

Question:
Balance the following chemical equations:
(i)
(ii)
(iii)

Answer:
(i)
(ii)
(iii)

2.

Question:
Write a balanced chemical equation for the following reaction:
Zinc reacts with dilute hydrochloric acid to give zinc chloride and hydrogen gas.

Answer:
The balanced chemical equation is:

Zn + 2HCl \rightarrow ZnCl_2 + H_2

3.

Question:
Identify the type of chemical reaction in each of the following:
(i) Burning of magnesium in air.
(ii) Decomposition of lead nitrate on heating.
(iii) Reaction between sodium and water.

Answer:
(i) Burning of magnesium in air is a combination reaction.
(ii) Decomposition of lead nitrate on heating is a decomposition reaction.
(iii) Reaction between sodium and water is a displacement reaction.

4.

Question:
Write the chemical equation for the following reactions and identify the type of reactions:
(i) Reaction between hydrogen and oxygen to form water.
(ii) Reaction between sodium and water.

Answer:
(i)
This is a combination reaction.

(ii)
This is a displacement reaction.

5.

Question:
What is meant by the term "combustion"? Explain with an example.

Answer:
Combustion is a chemical reaction in which a substance reacts with oxygen, usually releasing heat and light. For example:

2C_4H_{10} + 13O_2 \rightarrow 8CO_2 + 10H_2O

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