Physical And Chemical Changes Test

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Physical And Chemical Changes Test - 3

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Weekly Quiz Competition

Question 1
1 / -0

If we keep moistened iron nails for a few days, the iron nails get covered with a reddish-brown substance, which is different from iron. Which of the following is/are not the change(s) that take(s) place?

a. The state as well as the composition of iron changed.
b. The changes that took place were reversible.
c. A new substance was formed.

A
Only a

B
Only a and b

C
Only b

D
Only b and c

Solution

This is the correct option as the change that took place was not reversible. It was irreversible.
Question 2
1 / -0

Iron objects, such as the wheels of a bicycle, are coated with which of the following metals to give them a shining appearance?

A
Aluminium

B
Lead

C
Nickel

D
Copper

Solution

This is the correct option. Iron objects are coated with nickel to give them a shining appearance.
Question 3
1 / -0

Identify the incorrect statement(s).

Statement I: All physical changes are spontaneous, but chemical changes have to be induced.
Statement II: All changes, physical as well as chemical, involve energy exchanges.

A
Only I

B
Only II

C
Both I and II

D
None

Solution

Statement I is incorrect as spontaneity of a process depends on the conditions available. Many physical as well as chemical processes are spontaneous under standard conditions. For example, evaporation of water is spontaneous and so is the reaction of Na metal with the water vapour in the air. Statement II is correct as both physical and chemical processes involve energy changes.
Question 4
1 / -0

Which of the following are redox reactions?

I. Cu + 2H₂SO₄ → CuSO₄ + 2H₂O + SO₂
II. BaCI₂ + H₂SO₄ → BaSO₄ + 2HCI
III. Zn + H₂SO₄ → ZnSO₄ + H₂
IV. 2KNO₃ + H₂SO₄ → 2HNO₃ + K₂SO₄

A
II and IV only

B
I, II and III only

C
I and III only

D
I and IV only

Solution

Reactions I and III are redox reactions.
In reaction I, Cu is getting oxidised (oxidation state changes from 0 to +2) and S is getting reduced (oxidation state changes from +6 to +4).
In reaction III, Zn is getting oxidised (oxidation state changes from 0 to +2) and H⁺ is getting reduced (oxidation state changes from +1 to 0).
Question 5
1 / -0

When copper turnings are added to a clear solution of silver nitrate, a greyish deposit of silver is observed after some time. Silver gets precipitated and copper (II) nitrate is also formed. The reaction is an example of __________ reaction and ________ is more reactive than ________.

A
displacement, copper, silver

B
decomposition, copper, silver

C
decomposition, silver, copper

D
displacement, silver, copper

Solution

The chemical equation for the reaction is Cu (s) + 2AgNO₃(aq) → 2Ag (s) + Cu(NO₃)₂(aq).

In the given reaction, a metal (copper) is replacing another metal (silver) from the solution of its compound. Hence, the given reaction is an example of a displacement reaction. Copper replaces silver from the solution of its compound. Hence, copper is more reactive than silver.
Question 6
1 / -0

Zinc oxide (ZnO) reacts with carbon (C) to produce zinc (Zn) and carbon monoxide (CO). The balanced chemical equation for the given reaction is ZnO (s) + C (s) → Zn (s) + CO (g). Which of the following substances is reduced in the given reaction?

A
ZnO

B
C

C
CO

D
Zn

Solution

The given reaction is an example of a redox reaction. In a redox reaction, the substance that either gains oxygen or loses hydrogen is oxidised and the substance that loses oxygen or gains hydrogen is reduced. In the given reaction, zinc oxide (ZnO) loses oxygen to form zinc (Zn). Hence, ZnO is reduced in the given reaction.
Question 7
1 / -0

Consider the following reaction:

MnO₂ + 4HCl → MnCl₂ + Cl₂ + 2H₂O

Which of the following is getting oxidised in this reaction?

A
MnO₂

B
Cl₂

C
HCl

D
H₂O

Solution

In this reaction, hydrogen chloride is getting oxidised to form chlorine gas.
Question 8
1 / -0

Which of the following statements is not true about a substance that goes rancid?

A
Its smell changes.

B
Its taste changes.

C
Its colour changes.

D
It reduces in mass.

Solution

Rancidity is a term generally used to denote unpleasant odours, colour change and flavours in foods resulting from deterioration in the fat or oil portion of a food. There is no change in the mass observed, which is in agreement with the law of conservation of mass.
Question 9
1 / -0

Suppose, a reaction takes place between magnesium and oxygen to form magnesium oxide. Where will magnesium oxide be represented in the chemical equation?

A
L.H.S. of the arrow

B
R.H.S. of the arrow

C
Top of the arrow

D
Down the arrow

Solution

The reaction between Mg and oxygen is represented as:
2Mg + O₂ → 2MgO
Thus, MgO is the product and it is present on R.H.S of the arrow.
Question 10
1 / -0

Which of the following phenomena is not an indication of a chemical change?

A
Evolution of a gas

B
Change in shape

C
Change in temperature

D
Change in colour

Solution

Change in the shape of a substance does not indicate that a chemical change has taken place.

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Physical And Chemical Changes Test - 3

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Physical And Chemical Changes Test - 3

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Question 1

Only a

Only a and b

Only b

Only b and c

Solution

Question 2

Aluminium

Lead

Nickel

Copper

Solution

Question 3

Only I

Only II

Both I and II

None

Solution

Question 4

II and IV only

I, II and III only

I and III only

I and IV only

Solution

Question 5

displacement, copper, silver

decomposition, copper, silver

decomposition, silver, copper

displacement, silver, copper

Solution

Question 6

ZnO

C

CO

Zn

Solution

Question 7

MnO2

Cl2

HCl

H2O

Solution

Question 8

Its smell changes.

Its taste changes.

Its colour changes.

It reduces in mass.

Solution

Question 9

L.H.S. of the arrow

R.H.S. of the arrow

Top of the arrow

Down the arrow

Solution

Question 10

Evolution of a gas

Change in shape

Change in temperature

Change in colour

Solution

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MnO₂

Cl₂

H₂O