Changes Around Us Test

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Changes Around Us Test - 5

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Weekly Quiz Competition

Question 1
1 / -0

Which of the following changes can be reversed?

A
Milk Curd

B
Animal waste Manure

C
Mango Mango pickle

D
Steam Ice

Solution

Milk converted to curd, mango converted to mango pickle, and animal waste converted to manure are examples of the changes which cannot be reversed.
Inter-conversion of states of water, e.g., steam to ice, can easily be reversed by changing the temperature and pressure conditions.
Question 2
1 / -0

Which of the following statements about redox reactions is/are correct?

(i) A substance is said to be reduced if it gains oxygen during a reaction.
(ii) A substance is said to be oxidised if it gains electrons during a reaction.
(iii) A substance is said to be reduced if it loses oxygen during a reaction.
(iv) A substance is said to be reduced if it gains hydrogen during a reaction.

A
Only (i) and (ii)

B
Only (ii) and (iii)

C
Only (iii)

D
Only (iii) and (iv)

Solution

Oxidation can be defined as addition of oxygen or removal of hydrogen or loss of electrons.
Whereas, reduction can be defined as addition of hydrogen or removal of oxygen or gain of electrons.
Question 3
1 / -0

What is 'Z' in the given process?

Woollen yarn Z

A
Hand-knitted sweater

B
Sweater coat

C
Cardigan

D
Shawl

Solution

Hand-knitted woollen fabric can easily be undone to obtain the woollen yarn.
Question 4
1 / -0

Which of the given changes can be reversed?

A
Only A and B

B
Only A and C

C
Only C and D

D
Only B and D

Solution

Ice can be melted to form water again.
Also, the paper boat can be unfolded to get back the sheet of paper.
Hence, the changes represented in 'C' and 'D' are reversible.
Question 5
1 / -0

Which of the following is a balanced chemical equation of the reaction between carbon monoxide gas and hydrogen gas?

A
3CO(g) + 2H₂(g) CH₃OH()

B
CO(g) + 3H₂(g) CH₃OH()

C
CO(g) + 2H₂(g) 2CH₃OH()

D
CO(g) + 2H₂(g) CH₃OH()

Solution

The reaction given in option (4) is balanced as the number of atoms of different elements on both sides of the equation is equal. Whereas, the equations given in options (1), (2) and (3) are unbalanced because the number of atoms of different elements on both sides of equation is not equal.
Question 6
1 / -0

Why does silver chloride turn grey in the sunlight?

A
Due to decomposition of silver chloride into silver and chlorine

B
Due to displacement of silver by carbon present in the air

C
Due to displacement of chlorine by oxygen and formation of silver oxide

D
Due to formation of silver sulphide

Solution

White powder of silver chloride turns grey in the sunlight due to decomposition of silver chloride into silver and chlorine by utilizing light energy.

2AgCl (s) 2Ag (s) + Cl₂(g)

The reaction is also called photolysis.
Question 7
1 / -0

The ball and the ring made up of same metal and of same diameter are used to study the effect of heat on metals.

Which of the following statements is correct?

A
If only the ring is heated, the ball will pass through the heated ring.

B
If the ball is heated and allowed to cool, it will pass through the ring.

C
If both the ball and the ring are placed in cold water, the ball will pass through the ring.

D
If the ball is heated, it can pass through the ring.

Solution

When the ring is heated, it expands and the ball can pass through the ring.
If the ball is heated and then allowed to cool, it will return to its original size. The diameter of the ball and the ring being the same, the ball will not be able to pass through it.
Question 8
1 / -0

Which of the following reactions involves a physical change?

A
Photosynthesis

B
Respiration

C
Sublimation

D
Rusting

Solution

Sublimation is a process by which a solid on heating converts to vapour without going into the liquid state.
This is a physical change.
Question 9
1 / -0

Which of the following food items do/does not become rancid?

A
Potato chips

B
Vegetable oil

C
Fried sandwiches

D
Orange

Solution

Potato chips, vegetable oil and fried sandwiches become rancid due to oxidation of fatty acids present in them, but orange does not become rancid as it does not contain fatty acids.
Question 10
1 / -0

The characteristic feature of an oxidising agent is that it always

A
gains electrons

B
gets oxidised in a redox reaction

C
contains oxygen

D
is a non-metal

Solution

The characteristic feature of an oxidising agent is that it always gains electrons in a redox reaction and gets reduced.
Question 11
1 / -0

When a small amount of manganese dioxide is added to hydrogen peroxide, oxygen is evolved. This is an example of

A
reduction

B
oxidation

C
double decomposition

D
decomposition

Solution

When a small amount of manganese dioxide is added to hydrogen peroxide, oxygen is evolved. This is an example of a decomposition reaction.
H₂O₂ decomposes to H₂O and O₂; MnO₂ acts a catalyst in the reaction.
Question 12
1 / -0

In the reaction: Zn + H₂SO₄ ZnSO₄ + H₂, zinc undergoes

A
oxidation

B
reduction

C
hydrogenation

D
dehydrogenation

Solution

In the reaction: Zn + H₂SO₄ ZnSO₄ + H₂,zinc undergoes oxidation because its oxidation state increases from 0 to +2.
Question 13
1 / -0

If the sign '' is used in a chemical reaction, what does it indicate?

A
Temperature of the reactants is equal to the temperatures of the products.

B
Mass of all the reactant molecules is equal to the mass of all the product molecules.

C
All the reactants have converted to products.

D
Product molecules recombine to form reactant molecules and the reaction is reversible.

Solution

The sign indicates a reversible process in which the product molecules recombine to form reactant molecules and the reaction is reversible.
Question 14
1 / -0

Which of the following is a balanced chemical equation?

A
2Na + 2Cl₂ 2NaCl

B
2C + 3O₂ 5CO₂

C
2H₂ + 2Cl₂ 2HCl

D
2H₂ + O₂ 2H₂O

Solution

In a balanced chemical equation, the number of atoms of different elements on both sides of the equation is always equal.
In equation (4), the number of atoms (H and O) is equal on both the sides of the equation. Thus, equation (4) is a balanced chemical equation.
Question 15
1 / -0

Which of the following is true for all chemical reactions?

A
Heat is evolved.

B
There is a change in the volume.

C
Chemical bonds are broken and formed.

D
There is a change in mass.

Solution

In a chemical reaction, the reactants come into contact with each other, bonds between atoms in the reactants are broken, and atoms rearrange and form new bonds to form the products.