SCIENCE
“Aaj Padhle
Kal Exam Me
Yhi Ayega”
, Chapter 1
Q1. State the change in colour observed in following case
mentioning the reason:
Silver chloride is exposed to sunlight.
What happens when silver chloride is exposed to sunlight? Write a
chemical equation for this reaction. Also give one use of such a
reaction.
Solution
Photolytic Decomposition is the process by which silver chloride breaks
down into silver and chlorine when exposed to sunlight. Silver metal and
yellowish chlorine gas are the byproducts of the breakdown of white
silver chloride. The chemical reaction is given as follows:
Q2. In the electrolysis of water
a. Name the gas collected at the cathode and anode respectively.
b. Why is the volume of gas collected at one electrode double than
that at the other? Name this gas.
c. How will you test this gas ?
Solution
a. Hydrogen is collected at the cathode, and oxygen is collected at
the anode.
b. It is because H₂O contains hydrogen and oxygen in the ratio 2:1.
c. Bring a burning matchstick near the gas, if the gas burns with a
‘pop’ sound, the gas is H2.
Q3. Write the balanced chemical equation with the state symbols of
the following reaction:
(a) Solution of Barium chloride and Sodium sulphate in water react
to give insoluble Barium sulphate and the solution of Sodium
chloride.
(b) Sodium hydroxide solution (in water) reacts with hydrochloric
acid solution (in water) to produce sodium chloride and water.
/ PadhleAkshay
,Solution
(a) BaCl₂(aq) + Na₂SO₄(aq) → BaSO₄(s) + 2NaCl(aq)
(b) NaOH(aq) + HCl(aq) → NaCl(aq) + H₂O(l)
Q4. Define the term decomposition reaction. Give one example
each of thermal decomposition and electrolytic decomposition
reactions.
Solution
Decomposition reaction: The reaction in which a compound is broken
down into simpler elements or compounds:
CaCO₃(s) + heat → CaO(s) + CO₂(g)
2H₂O(l) + Electric current →2H₂(g) +O₂(g)
Q5. With the help of an appropriate example, justify that some of
the chemical reactions are determined by:
(a) Change in temperature
(b) Evolution of a gas
(c) Change in color and give the chemical equation for the reaction
involved in each case
Solution
(a) The chemical reaction between quicklime and water to form
slaked lime is characterized by a rise in temperature (change in
temperature).
CaO(s) + H₂O(l) → Ca(OH)₂(aq) + Heat
(b) The chemical reaction between zinc and dilute sulphuric acid is
characterized by the evolution of H₂ gas.
Zn + H₂SO₄ → ZnSO₄ + H₂
(c) When a piece of iron metal is placed in a copper sulfate solution,
iron sulfate solution and copper metal are formed. Additionally, the
deep blue color of the copper solution fades, and a light green
solution forms.
CuSO₄(aq) + Fe(s) Blue solution → FeSO₄(aq) + Cu(s) Green solution
Q6. (a) Mention the four information given by an equation.
(b) State the law of conservation of mass as applicable in a
chemical reaction.
/ padhle.akshay
, Solution
(a)
(i) Change in state
(ii) Catalyst involved
(iii) Physical state of reactants and products
(iv) Conditions such as temperature, pressure, etc.
(b) The total mass of elements present in the reactants has to be
equal to the mass of elements present in the products in a chemical
reaction.
Q7. Identify the type of chemical reaction in the following
statement and define each of them:
a. Digestion of food in our body.
b. Rusting of iron.
c. Heating of manganese dioxide with aluminum powder.
d. The blue color of copper sulphate solution disappears when iron
filings are added.
e. Dilute hydrochloric acid is added to sodium hydroxide solution
to form sodium chloride and water.
Solution
a. Decomposition reaction: It is a process in which a compound is
broken down into simple substances.
b. Oxidation: The process in which oxygen is added or electrons are
lost.
c. Displacement reaction: The reaction in which a more reactive
element can displace a less reactive element from its salt solution.
Oxidation and Reduction occur simultaneously in the rusting of iron.
and its salt solution. Oxidation and Reduction are taking placee
simultaneously in the rusting of iron.
d. Displacement reaction: The reaction in which a more reactive
element can displace a less reactive element.
e. Neutralization reaction: The reaction in which acid reacts with a
base to form salt and water.
Q8. Why should a magnesium ribbon be cleaned before burning in
air?
Solution
/ PadhleAkshay
“Aaj Padhle
Kal Exam Me
Yhi Ayega”
, Chapter 1
Q1. State the change in colour observed in following case
mentioning the reason:
Silver chloride is exposed to sunlight.
What happens when silver chloride is exposed to sunlight? Write a
chemical equation for this reaction. Also give one use of such a
reaction.
Solution
Photolytic Decomposition is the process by which silver chloride breaks
down into silver and chlorine when exposed to sunlight. Silver metal and
yellowish chlorine gas are the byproducts of the breakdown of white
silver chloride. The chemical reaction is given as follows:
Q2. In the electrolysis of water
a. Name the gas collected at the cathode and anode respectively.
b. Why is the volume of gas collected at one electrode double than
that at the other? Name this gas.
c. How will you test this gas ?
Solution
a. Hydrogen is collected at the cathode, and oxygen is collected at
the anode.
b. It is because H₂O contains hydrogen and oxygen in the ratio 2:1.
c. Bring a burning matchstick near the gas, if the gas burns with a
‘pop’ sound, the gas is H2.
Q3. Write the balanced chemical equation with the state symbols of
the following reaction:
(a) Solution of Barium chloride and Sodium sulphate in water react
to give insoluble Barium sulphate and the solution of Sodium
chloride.
(b) Sodium hydroxide solution (in water) reacts with hydrochloric
acid solution (in water) to produce sodium chloride and water.
/ PadhleAkshay
,Solution
(a) BaCl₂(aq) + Na₂SO₄(aq) → BaSO₄(s) + 2NaCl(aq)
(b) NaOH(aq) + HCl(aq) → NaCl(aq) + H₂O(l)
Q4. Define the term decomposition reaction. Give one example
each of thermal decomposition and electrolytic decomposition
reactions.
Solution
Decomposition reaction: The reaction in which a compound is broken
down into simpler elements or compounds:
CaCO₃(s) + heat → CaO(s) + CO₂(g)
2H₂O(l) + Electric current →2H₂(g) +O₂(g)
Q5. With the help of an appropriate example, justify that some of
the chemical reactions are determined by:
(a) Change in temperature
(b) Evolution of a gas
(c) Change in color and give the chemical equation for the reaction
involved in each case
Solution
(a) The chemical reaction between quicklime and water to form
slaked lime is characterized by a rise in temperature (change in
temperature).
CaO(s) + H₂O(l) → Ca(OH)₂(aq) + Heat
(b) The chemical reaction between zinc and dilute sulphuric acid is
characterized by the evolution of H₂ gas.
Zn + H₂SO₄ → ZnSO₄ + H₂
(c) When a piece of iron metal is placed in a copper sulfate solution,
iron sulfate solution and copper metal are formed. Additionally, the
deep blue color of the copper solution fades, and a light green
solution forms.
CuSO₄(aq) + Fe(s) Blue solution → FeSO₄(aq) + Cu(s) Green solution
Q6. (a) Mention the four information given by an equation.
(b) State the law of conservation of mass as applicable in a
chemical reaction.
/ padhle.akshay
, Solution
(a)
(i) Change in state
(ii) Catalyst involved
(iii) Physical state of reactants and products
(iv) Conditions such as temperature, pressure, etc.
(b) The total mass of elements present in the reactants has to be
equal to the mass of elements present in the products in a chemical
reaction.
Q7. Identify the type of chemical reaction in the following
statement and define each of them:
a. Digestion of food in our body.
b. Rusting of iron.
c. Heating of manganese dioxide with aluminum powder.
d. The blue color of copper sulphate solution disappears when iron
filings are added.
e. Dilute hydrochloric acid is added to sodium hydroxide solution
to form sodium chloride and water.
Solution
a. Decomposition reaction: It is a process in which a compound is
broken down into simple substances.
b. Oxidation: The process in which oxygen is added or electrons are
lost.
c. Displacement reaction: The reaction in which a more reactive
element can displace a less reactive element from its salt solution.
Oxidation and Reduction occur simultaneously in the rusting of iron.
and its salt solution. Oxidation and Reduction are taking placee
simultaneously in the rusting of iron.
d. Displacement reaction: The reaction in which a more reactive
element can displace a less reactive element.
e. Neutralization reaction: The reaction in which acid reacts with a
base to form salt and water.
Q8. Why should a magnesium ribbon be cleaned before burning in
air?
Solution
/ PadhleAkshay
