Redox Reactions Online Objective Test | Redox Reactions Online Objective Test

# Redox Reactions # CBSE 11TH CHEMISTRY Prepare / Learn

Q1. In Daniell cell, direction of current is

A. towards anode

B. towards centre

C. in the same direction of electron flow

D. opposite to the direction of electron flow

Answer : Option D
Explaination / Solution:

Current is taken at the direction in which positive charge is flowing, but electrons are negatively charged. So, the direction of current and the direction of electron flow is opposite.

# Redox Reactions # CBSE 11TH CHEMISTRY Prepare / Learn

Q2. The flow of current is possible in Daniel cell only

A. if the zinc and copper rods are connected by the platinum wire only

B. if there is a potential difference between the copper and zinc electrodes

C. if the transfer of electrons does take place directly from Zn to Cu2+

D. if the zinc and copper rods are connected by a salt bridge only

Answer : Option B
Explaination / Solution:

The flow of current is possible only due to potential difference.

# Redox Reactions # CBSE 11TH CHEMISTRY Prepare / Learn

Q3. In oxygen difluoride

(O F_{2})

and dioxygen difluoride

(O_{2} F_{2})

, the oxygen is assigned an oxidation number of

A. +2 and +1

B. +2

C. +4 and +3

D. +2 and +4

Answer : Option A
Explaination / Solution:

Oxidation state of O in OF2 is +2 and O2F2 is +1. Because the number assigned to oxygen will depend upon the bonding state of oxygen.

# Redox Reactions # CBSE 11TH CHEMISTRY Prepare / Learn

Q4. Oxidation number of −1/2 is assigned to oxygen atom in

A. when oxygen is bonded to metals

B. superoxides

C. peroxides

D. when oxygen is bonded to fluorine

Answer : Option B
Explaination / Solution:

In the superoxide ion, O2−, the oxygen has an oxidation number of −1/2. The stability of metal superoxides depends on the size and the electropositive character of the metal. The larger the metal and the more electropositive it is, the greater the stability of its superoxide.

# Redox Reactions # CBSE 11TH CHEMISTRY Prepare / Learn

Q5. Assign oxidation number to P in

Na H_{2} P O_{4}

A. +1

B. +6

C. +4

D. 5.0

Answer : Option D
Explaination / Solution:

Oxidation state of P in NaH2PO4 is +5.

Let the oxidation number of P be x. As we already know oxidation number of other atoms so we can calculate that of P too.

Na = +1

H= +1 (+2 for hydrogen molecule)

O = -2

Now calculating oxidation number of P:-

1 +2 + x +(-8) = 0

On solving we get x= +5.

# Redox Reactions # CBSE 11TH CHEMISTRY Prepare / Learn

Q6. Assign oxidation number to S in

KAl {(S O_{4})}_{2} . 12 H_{2} O

A. +4

B. +12

C. +5

D. 6.0

Answer : Option D
Explaination / Solution:

Oxidation state of S in KAl(SO4)2 is +6

# Redox Reactions # CBSE 11TH CHEMISTRY Prepare / Learn

Q7.

If an excess of $P_{4}$ is treated with $F_{2}$ , then_____will be produced wherein the oxidation number of P is +3. The compound is

A. PF5

B. PF6

C. PF

D. PF3

Answer : Option D
Explaination / Solution:

Whenever a reaction between an oxidising agent and a reducing agent is carried out, a compound of lower oxidation state is formed if the reducing agent is in excess and a compound of higher oxidation state is formed if the oxidising agent is in excess. This can be illustrated as follows:

P4 and F2 are reducing and oxidising agents respectively. If an excess of P4 is treated with F2, then PF3 will be produced, wherein the oxidation number (O.N.) of P is +3.
$P F_{4} (e x c e s s) + F_{2} \to P F_{3}$

# Redox Reactions # CBSE 11TH CHEMISTRY Prepare / Learn

Q8. Which of the following is not an example of redox reaction?

A. BaCl2+H2SO4→BaSO4+2HCl

B. 2K + F2 → 2KF

C. CuO +H2→ Cu +H2O

D. Fe2O3+3CO→2Fe+3CO2

Answer : Option A
Explaination / Solution:

The reaction is not redox because there is no oxidation or reduction of any element (i.e. no change in oxidation state/number).

Ba in BaCl2 is at a +2 charge because it is in group 2. On the other side of the equation Ba in BaSO4 is still +2. Cl2 on the first side of the equation is -2 (as 2 chlorines) and Cl is -2 on the other side as there are 2 of them.

H on both sides are both +1 (but technically +2 as there are two of them).

SO4 does not change oxidation number and always remains -2.

So, the reaction is not a redox reaction.

# Redox Reactions # CBSE 11TH CHEMISTRY Prepare / Learn

Q9. Electrochemical processes for extraction of highly reactive metals and non-metals involves one of the following. Choose the most appropriate option.

A. reaction with inert gases

B. oxidation processes

C. reduction processes

D. redox processes

Answer : Option D
Explaination / Solution:

It involves redox process.

# Redox Reactions # CBSE 11TH CHEMISTRY Prepare / Learn

Q10.

2 N a^{+} (s) \to 2 N a^{+} (g) + 2 e^{-}

H 2 (g) + 2 e^{-} n ? 2 H + (g)

H 2 (g) + 2 e^{-} n ? 2 H + (g)

H 2 (g) + 2 e^{-} n ? 2 H + (g)

A. hydrogen is oxidised

B. sodium is reduced

C. electronegativity of sodium determines the direction of the reaction

D. sodium is oxidised and hydrogen is reduced

Answer : Option D
Explaination / Solution:

sodium is oxidized and hydrogen is reduced.

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