19 + Interview Questions in OXIDATION IN GENERAL AWARENESS Page 1 InterviewSolution

1.	What is the maximum oxidation state of sulphur ?
Answer» The maximum oxidation state of sulphur is +6.

Discussion

2.	In the following reaction 2FeCl3 +SnCl2 ➝ 2FeCl2 +SnCl4The substance which get reduced is :(a) Sn+2(b) Fe+2(c) Sn+4(d) Fe+3
Answer» The answer is (d) Fe⁺³

Discussion

3.	How to balance a reaction taking place in basic medium by ion electron method ?
Answer» There are following steps used-to balance a reaction taking place in basic medium by ion electron method : Step I: Write the skeletal equation and indicate the oxidation number of all the elements. Step II: Find out the species which are oxidised and which are reduced. Step III: Split the equation in two half reactions i.e. oxidation half reaction and reduction half reaction Step IV: Balance the two half reactions separately by using following steps : (i) First of all, balance the atoms of the elements which have undergone a change in oxidation number (ii) Add electrons to whatever side in necessary to make up the difference in oxidation number in each half reaction. (iii) Balance change by adding OH^–. (iv) Balance oxygen atoms by adding required number of H₂O molecules to the side deficient in O-atoms. (v) H-atoms are balanced by adding H₂O molecules equal in number to the deficiency of H atoms and equal number of OH^– ions are included in opposite side of the equation. Step V: The two half reactions are multiplied by suitable integers to balance the number of electrons. The half reaction, are then added up.

3.

How to balance a reaction taking place in basic medium by ion electron method ?

Answer»

There are following steps used-to balance a reaction taking place in basic medium by ion electron method :

Step I: Write the skeletal equation and indicate the oxidation number of all the elements.

Step II: Find out the species which are oxidised and which are reduced.

Step III: Split the equation in two half reactions i.e. oxidation half reaction and reduction half reaction

Step IV: Balance the two half reactions separately by using following steps :

(i) First of all, balance the atoms of the elements which have undergone a change in oxidation number

(ii) Add electrons to whatever side in necessary to make up the difference in oxidation number in each half reaction.

(iii) Balance change by adding OH^–.

(iv) Balance oxygen atoms by adding required number of H₂O molecules to the side deficient in O-atoms.

(v) H-atoms are balanced by adding H₂O molecules equal in number to the deficiency of H atoms and equal number of OH^– ions are included in opposite side of the equation.

Step V: The two half reactions are multiplied by suitable integers to balance the number of electrons. The half reaction, are then added up.

Discussion

4.

Explain the difference between oxidation state and valency of an element.

Answer»

	Oxidation state		Valency
(1)	In an atom or ion of a substance, the number of effective charge present on an element is called oxidation state of an element.	(1)	The valency of an element is a measure of its power with other atoms.
(2)	The value of oxidation state may be positive, negative or zero.	(2)	Valency is always +ve. Inert gases have valency due to complete octet zero.
(3)	In covalent compounds, oxidation state of an element is variable	(3)	In covalent compounds, the valency of an element is generally constant.

Discussion

5.	Calculate the oxidation number :(i) Mo in (NH4)2MoO4(ii) Ni in [Ni(CN)4]2-
Answer» (i) Suppose oxidation number of Mo in (NH₄)₂MoO₄ = x 2 (+1) + x+ 4 (-2) = 0 2 + x – 8 = 0 x – 6 = 0 x = + 6 (ii) Suppose, oxidation number of Ni in [Ni(CN)₄]^2- = + x x + 4 (-1) = -2 x – 4 = -2 x = -2 + 4 = +2 ∴ Oxidation number of Ni in [Ni(CN)₄ ]² = + 2

5.

Calculate the oxidation number :(i) Mo in (NH4)2MoO4(ii) Ni in [Ni(CN)4]2-

Answer»

(i) Suppose oxidation number of Mo in (NH₄)₂MoO₄ = x
2 (+1) + x+ 4 (-2) = 0
2 + x – 8 = 0
x – 6 = 0
x = + 6

(ii) Suppose, oxidation number of Ni in [Ni(CN)₄]^2- = + x
x + 4 (-1) = -2
x – 4 = -2
x = -2 + 4 = +2
∴ Oxidation number of Ni in [Ni(CN)₄ ]² = + 2

Discussion

6.	Identify the reducing agent in the following reaction:5H2O2 + Br2 → 2HBrO3 + 4H2O
Answer» Br₂ acts as reducing agent in the given reaction, because it reduces hydrogen peroxide into water. H₂O₂ + 2H⁺ + 2e^– → 2H₂O (reduction)

Discussion

7.	Oxidation is a process :(a) In which electrons are accepted(b) In which electronegative element is added(c) In which electro positive element is added(d) In which oxygen is released
Answer» (b) In which electronegative element is added

Discussion

8.	What is cell potential ?
Answer» The cell potential is the measure of potential difference between two half cell in an electrochemical cell. It is represent by the symbol E-cell.

Discussion

9.	What is the oxidation number of Li in LiAlH4 ?
Answer» x + 3 + 4 (-1) = 0 x + 3 – 4 = 0 x – 1 = 0 x = 1 ∴ The oxidation number of Li : LiAlH₄ is + 1.

Discussion

10.	In which of the following pair of compounds, oxidation number of chromium is same(a) K2CrO4 and KCrO2(b) KCrO2 and Cr(CO)6(c) K2Cr2O7 and Cr(CO)4(d) K2Cr2O7 and K2CrO4
Answer» (b) KCrO₂ and Cr(CO)₆

Discussion

11.	The oxidation number of carbon in diamond is :(a) Zero(b) +4(c) -4(d) +2
Answer» The answer is (a) Zero

Discussion

12.	Calculate the oxidation number of Fe in K4 [Fe(CN)6]
Answer» 4 (+1) + x + 6 (-1) - 0 4 + x – 6 = 0 x – 2 = 0 x = + 2 ∴ The oxidation number Fe in K₄ [Fe (CN)₆] is + 2.

Discussion

13.	Which of the following is a redox reaction ?(a) 2FeCl3 + SnCl2 ➝ 4 2FeCl2 + SnCl4(b) AsNO3 + HCl ➝ AsCl + HNO3(c) 2Kl + Pb(NO)3 ➝ 2KNO3 +Pbl2(d) BaCl2 + H2SO4 ➝ BaSO4 + 2HCl
Answer» (a) 2FeCl₃ + SnCl₂ → 4FeCl₂ + SnCl₄

Discussion

14.	In the given structure the electronegativity of Y is more then Z. Find the oxidation Number of Z.\(X-Y-\overset{\overset{X}{\|}}{\underset{\underset{X}{\|}}{Z}}-Y-X\)
Answer» In this structure, the oxidation number of Z is zero.

Discussion

15.	Calculate the value of x in the following equation :CIO– + H2O + xe– ➝ + Cl + 20H–
Answer» The value of x is 2 in the given reaction: CIO^– + H₂O + 2e^– → Cl^– + 2OH^– gain of two electrons in this reaction

Discussion

16.	Write the oxidation number of nitrogen in ammonium nitrate.
Answer» NH₄NO₃ x + 4 × (+1) + (-1)= 0 × + 4 - 1= 0 x = -4 + 1 x= -3 ∴ The oxidation number of nitrogen in ammonium nitrate is + 5 and -3.

Discussion

17.	What do you mean by redox reaction ?
Answer» Redox reaction is the reaction in which both oxidation and reduction take place.

Discussion

18.	Which is of two F or I shows both positive and negative oxidation states ?
Answer» I (iodine) shows both positive and negative oxidation states.

Discussion

19.	Arrange the following in increasing order of oxidation states of Mn, K2MnO4 , MnO2 , KMnO4
Answer» Oxidation state of Mn in K₂MnO₄ 1(2) + x + 4 (-2) = 0 2 + x – 8 = 0 x = 8 – 2 x = +6 Oxidation state of Mn in MnO₂ x + 2 (-2) =0 x – 4 = 0 x= +4 Oxidation state of Mn in KMnO₄ 1 + x + 4 (-2) = 0 1 + x – 8 = 0 x – 7 = 0 x = + 7 ∴ Increasing order of oxidation states of Mn, MnO₂ < K₂MnO₄ < KMnO₄

Discussion

Explore topic-wise InterviewSolutions in .

What is the maximum oxidation state of sulphur ?

In the following reaction 2FeCl3 +SnCl2 ➝ 2FeCl2 +SnCl4The substance which get reduced is :(a) Sn+2(b) Fe+2(c) Sn+4(d) Fe+3

How to balance a reaction taking place in basic medium by ion electron method ?

Explain the difference between oxidation state and valency of an element.

Calculate the oxidation number :(i) Mo in (NH4)2MoO4(ii) Ni in [Ni(CN)4]2-

Identify the reducing agent in the following reaction:5H2O2 + Br2 → 2HBrO3 + 4H2O

Oxidation is a process :(a) In which electrons are accepted(b) In which electronegative element is added(c) In which electro positive element is added(d) In which oxygen is released

What is cell potential ?

What is the oxidation number of Li in LiAlH4 ?

In which of the following pair of compounds, oxidation number of chromium is same(a) K2CrO4 and KCrO2(b) KCrO2 and Cr(CO)6(c) K2Cr2O7 and Cr(CO)4(d) K2Cr2O7 and K2CrO4

The oxidation number of carbon in diamond is :(a) Zero(b) +4(c) -4(d) +2

Calculate the oxidation number of Fe in K4 [Fe(CN)6]

Which of the following is a redox reaction ?(a) 2FeCl3 + SnCl2 ➝ 4 2FeCl2 + SnCl4(b) AsNO3 + HCl ➝ AsCl + HNO3(c) 2Kl + Pb(NO)3 ➝ 2KNO3 +Pbl2(d) BaCl2 + H2SO4 ➝ BaSO4 + 2HCl

In the given structure the electronegativity of Y is more then Z. Find the oxidation Number of Z.\(X-Y-\overset{\overset{X}{|}}{\underset{\underset{X}{|}}{Z}}-Y-X\)

Calculate the value of x in the following equation :CIO– + H2O + xe– ➝ + Cl + 20H–

Write the oxidation number of nitrogen in ammonium nitrate.

What do you mean by redox reaction ?

Which is of two F or I shows both positive and negative oxidation states ?

Arrange the following in increasing order of oxidation states of Mn, K2MnO4 , MnO2 , KMnO4