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Chemistry
Chemical Reactions and Equations
NCERT Solutions
NCERT Solutions
Chemical Reactions and Equations
28 Solutions
Exercise:
All Exercises
Exercises
In-text Questions (Page 13)
In-text Questions (Page 15)
In-text Questions (Page 6)
Q1
Exercises
Which of the statements about the reaction below are incorrect?
2
P
b
O
(
s
)
+
C
(
s
)
→
2
P
b
(
s
)
+
C
O
2
(
g
)
2PbO(s) + C(s) \rightarrow 2Pb(s) + CO_2(g)
2
P
b
O
(
s
)
+
C
(
s
)
→
2
P
b
(
s
)
+
C
O
2
(
g
)
(a) Lead is getting reduced. (b) Carbon dioxide is getting oxidised. (c) Carbon is getting oxidised. (d) Lead oxide is getting reduced.
(i)
(a)
and (b)
(ii)
(a)
and (c)
(iii)
(a)
, (b) and (c)
(iv)
all
Q2
Exercises
F
e
2
O
3
+
2
A
l
→
A
l
2
O
3
+
2
F
e
Fe_2O_3 + 2Al \rightarrow Al_2O_3 + 2Fe
F
e
2
O
3
+
2
A
l
→
A
l
2
O
3
+
2
F
e
The above reaction is an example of a
(a)
combination reaction.
(b)
double displacement reaction.
(c)
decomposition reaction.
(d)
displacement reaction.
Q3
Exercises
What happens when dilute hydrochloric acid is added to iron fillings? Tick the correct answer.
(a)
Hydrogen gas and iron chloride are produced.
(b)
Chlorine gas and iron hydroxide are produced.
(c)
No reaction takes place.
(d)
Iron salt and water are produced.
Q4
Exercises
What is a balanced chemical equation? Why should chemical equations be balanced?
Q5
Exercises
Translate the following statements into chemical equations and then balance them.
(a)
Hydrogen gas combines with nitrogen to form ammonia.
(b)
Hydrogen sulphide gas burns in air to give water and sulpur dioxide.
(c)
Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate.
(d)
Potassium metal reacts with water to give potassium hydroxide and hydrogen gas.
Q6
Exercises
Balance the following chemical equations.
(a)
H
N
O
3
+
C
a
(
O
H
)
2
→
C
a
(
N
O
3
)
2
+
H
2
O
HNO_3 + Ca(OH)_2 \rightarrow Ca(NO_3)_2 + H_2O
H
N
O
3
+
C
a
(
O
H
)
2
→
C
a
(
N
O
3
)
2
+
H
2
O
(b)
N
a
O
H
+
H
2
S
O
4
→
N
a
2
S
O
4
+
H
2
O
NaOH + H_2SO_4 \rightarrow Na_2SO_4 + H_2O
N
a
O
H
+
H
2
S
O
4
→
N
a
2
S
O
4
+
H
2
O
(c)
N
a
C
l
+
A
g
N
O
3
→
A
g
C
l
+
N
a
N
O
3
NaCl + AgNO_3 \rightarrow AgCl + NaNO_3
N
a
Cl
+
A
g
N
O
3
→
A
g
Cl
+
N
a
N
O
3
(d)
B
a
C
l
2
+
H
2
S
O
4
→
B
a
S
O
4
+
H
C
l
BaCl_2 + H_2SO_4 \rightarrow BaSO_4 + HCl
B
a
C
l
2
+
H
2
S
O
4
→
B
a
S
O
4
+
H
Cl
Q7
Exercises
Write the balanced chemical equations for the following reactions.
(a)
Calcium hydroxide + Carbon dioxide → Calcium carbonate + Water
(b)
Zinc + Silver nitrate → Zinc nitrate + Silver
(c)
Aluminium + Copper chloride → Aluminium chloride + Copper
(d)
Barium chloride + Potassium sulphate → Barium sulphate + Potassium chloride
Q8
Exercises
Write the balanced chemical equation for the following and identify the type of reaction in each case.
(a)
Potassium bromide(aq) + Barium iodide(aq) → Potassium iodide(aq) + Barium bromide(s)
(b)
Zinc carbonate(s) → Zinc oxide(s) + Carbon dioxide(g)
(c)
Hydrogen(g) + Chlorine(g) → Hydrogen chloride(g)
(d)
Magnesium(s) + Hydrochloric acid(aq) → Magnesium chloride(aq) + Hydrogen(g)
Q9
Exercises
What does one mean by exothermic and endothermic reactions? Give examples.
Q10
Exercises
Why is respiration considered an exothermic reaction? Explain.
Q11
Exercises
Why are decomposition reactions called the opposite of combination reactions? Write equations for these reactions.
Q12
Exercises
Write one equation each for decomposition reactions where energy is supplied in the form of heat, light or electricity.
Q13
Exercises
What is the difference between displacement and double displacement reactions? Write equations for these reactions.
Q14
Exercises
In the refining of silver, the recovery of silver from silver nitrate solution involved displacement by copper metal. Write down the reaction involved.
Q15
Exercises
What do you mean by a precipitation reaction? Explain by giving examples.
Q16
Exercises
Explain the following in terms of gain or loss of oxygen with two examples each.
(a)
Oxidation
(b)
Reduction
Q17
Exercises
A shiny brown coloured element 'X' on heating in air becomes black in colour. Name the element 'X' and the black coloured compound formed.
Q18
Exercises
Why do we apply paint on iron articles?
Q19
Exercises
Oil and fat containing food items are flushed with nitrogen. Why?
Q20
Exercises
Explain the following terms with one example each.
(a)
Corrosion
(b)
Rancidity
Q1
In-text Questions (Page 13)
A solution of a substance 'X' is used for whitewashing.
(i)
Name the substance 'X' and write its formula.
(ii)
Write the reaction of the substance 'X' named in (i) above with water.
Q2
In-text Questions (Page 13)
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.
Q1
In-text Questions (Page 15)
Why does the colour of copper sulphate solution change when an iron nail is dipped in it?
Q2
In-text Questions (Page 15)
Give an example of a double displacement reaction other than the one given in Activity 1.10.
Q3
In-text Questions (Page 15)
Identify the substances that are oxidised and the substances that are reduced in the following reactions.
(i)
4
N
a
(
s
)
+
O
2
(
g
)
→
2
N
a
2
O
(
s
)
4Na(s) + O_2(g) \rightarrow 2Na_2O(s)
4
N
a
(
s
)
+
O
2
(
g
)
→
2
N
a
2
O
(
s
)
(ii)
C
u
O
(
s
)
+
H
2
(
g
)
→
C
u
(
s
)
+
H
2
O
(
l
)
CuO(s) + H_2(g) \rightarrow Cu(s) + H_2O(l)
C
u
O
(
s
)
+
H
2
(
g
)
→
C
u
(
s
)
+
H
2
O
(
l
)
Q1
In-text Questions (Page 6)
Why should a magnesium ribbon be cleaned before burning in air?
Q2
In-text Questions (Page 6)
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
Q3
In-text Questions (Page 6)
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.
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