The p-Block Elements

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Question 1

 Which is the correct statement for the given acids?

  • Phosphinic acid is a monoprotic acid while phosphonic acid is a diprotic acid.

  • phosphinic acid is a diprotic acid while phosphonic acid is a monoprotic acid

  • Both are triprotic acids

  • Both are diprotic acids

Solution

A.

Phosphinic acid is a monoprotic acid while phosphonic acid is a diprotic acid.

Phosphinic acid

Due to the presence of one replaceable proton in phosphinic acid, it is monoprotic acid. and due to the presence of two replaceable proton in phosphinic acid, it is diprotic acid.

Question 2

Acidity of diprotic acids in aqueous solutions increases in the order

  • H2S < H2Se< H2Te

  • H2Se <H2S <H2Te

  • H2Te <H2S < H2Se

  • H2Se < H2Te <H2S

Solution

A.

H2S < H2Se< H2Te

Acidic strength of hydrides increases as the size of central atom increases which weakens the M-H bond. Since, the size increases from S to Te thus acidic strength follows the order
H2S <H2Se <H2Te

Question 3

Among the following which is the strongest oxidising agent?

  • F2

  • Br2

  • I2

  • Cl2

Solution

A.

F2

An element having higher tendency to get reduced or to accept an electron is a strong oxidising agent.
Fluorine is the most electronegative element because electronegativity decrease on moving down the group. Hence, it gets reduced readily into F- ion and is a strongest oxidising agent.

Question 4

Among the following, the correct order of acidity is

  • HClO<HClO2<HClO3<HClO4

  • HClO2<HClO<HClO3<HClO4

  • HClO4<HClO<HClO <HClO3

  • HClO3<HClO4<HClO2<HClO

Solution

A.

HClO<HClO2<HClO3<HClO4

As the oxidation state of halogen increases the acidity of oxyacid also increases.
HClO: Oxidation state of Cl =+1
HClO2 : Oxidation state of Cl =+3
HClO3 : Oxidation state of Cl = +5
HClO4 : Oxidation state of Cl = +7
Therefore, the correct order of acidity would be 
HClO2<HClO<HClO3<HClO4

Question 5

For the following:
(i) I-  (ii) Cl-   (iii) Br-

the increasing order of nucleophilicity would be: 

  • I- < Br- < Cl-

  • Cl- < Br- < I-

  • I- < Cl- < Br-

  • Br- < Cl- < I-

Solution

A.

I- < Br- < Cl-

Halogens are the most reactive elements. High reactivity is due to their low dissociation energy. Further among halogen reactivity decreases as we move down the group. So, the correct order of nucleophilicity would be
I- < Br- < Cl-