Page 11 - NCERT Science Class 10 English Medium

Q U E S T I O N S

1. Why should a magnesium ribbon be cleaned before burning in air?
2. Write the balanced equation for the following chemical reactions.
(i) Hydrogen + Chlorine → Hydrogen chloride
(ii) Barium chloride + Aluminium sulphate → Barium sulphate +
Aluminium chloride
(iii) Sodium + Water → Sodium hydroxide + Hydrogen ?
3. Write a balanced chemical equation with state symbols for the
following reactions.
(i) Solutions of barium chloride and sodium sulphate in water react
to give insoluble barium sulphate and the solution of sodium
chloride.
(ii) Sodium hydroxide solution (in water) reacts with hydrochloric
acid solution (in water) to produce sodium chloride solution and
water.

1.2 TYPES OF CHEMICAL REAAL REACTIONSCTIONS
OF
1.2 TYPES OF CHEMICAL REACTIONS
CHEMICAL REA
1.2 TYPES OF CHEMICTYPES OF CHEMICAL REACTIONSCTIONS
1.2
1.2 TYPES
We have learnt in Class IX that during a chemical reaction atoms of one
element do not change into those of another element. Nor do atoms
disappear from the mixture or appear from elsewhere. Actually, chemical
reactions involve the breaking and making of bonds between atoms to
produce new substances. You will study about types of bonds formed
between atoms in Chapters 3 and 4.
1.2.1 Combination Reaction

Activity
Activity 1.4
Activity 1.4
Activity 1.41.4
Activity 1.4
n Take a small amount of calcium oxide
or quick lime in a beaker.
n Slowly add water to this.
n Touch the beaker as shown in Fig. 1.3.
n Do you feel any change in temperature?
Figure 1.3
Figure 1.3
Figure 1.3
Figure 1.3
Figure 1.3
Formation of slaked
lime by the reaction of
calcium oxide with Calcium oxide reacts vigorously with water to produce slaked lime
water (calcium hydroxide) releasing a large amount of heat.
CaO(s) + H O(l) → Ca(OH) (aq) + Heat (1.13)
2 2
(Quick lime) (Slaked lime)
In this reaction, calcium oxide and water combine to form a single
product, calcium hydroxide. Such a reaction in which a single product
is formed from two or more reactants is known as a combination reaction.

6 Science

2024-25