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Physical Chemistry

Language of Chemistry Stoichiometry Atomic Structure Oxidation and Reduction Periodic Table Acid and Base Electronic Theory of Valency Equivalent Weight and Atomic Weight

Physical Chemistry-II

Non-Metals

Introduction Halogens Nitrogen Sulphur Oxygen

Inorganic Chemistry

Sulphur

Introduction

Symbol: $S$
Valency: $2, 4 an d 6$
Atomic Number: $16$
Atomic mass: $32$
Electronic Configuration: $1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{4}$
It lies in group $V I A$ along with $O, S, S e an d T e$ . $V I A$ elements are collectively called Chalcogens (means ore forming).
It is known from ancient period as brimstone i.e. 'burning stone'.
It occurs free in nature in a volcanic area. In combined state, it is found as sulphides and sulphates of metal in the form of $F e S_{2}, P b S, Z n S, C u F e S_{2}, H g S$ , etc.

Properties:

It is pale yellow.
It is insoluble in water but dissolves in $C S_{2}$ and $C_{6} H_{6}$ .
It’s molecular formula is $S_{8}$ .

Allotropes of Sulphur

A)Crystalline forms:

1) Rhombic or $(α - S u lp h u r)$ :

- Most Stable form of Suphur.

- Shape of crystal = Octahedrol

- Molecular Formula = $S_{8}$

- Shape of Molecule = Crown, chair and Boat

- Insoluble in water but soluble in $C S_{2}$ .

-Bad conductor of heat and electricity.

-Pale yellow in colour but transparent.

-Melts at $11 4^{\circ} C$ .Its density is $2.05$ .

2) Monoclinic Sulphur or Prismatic or $(β - S u lp h u r)$ :

-It is prepared by melting Rhombic Sulphur at $9 6^{\circ} C$ followed by cooling.

-It is deep yellow crystalline solid but opaque.

-It is insoluble in Water but soluble in $C S_{2}$ .

-Least Stable Form.

-Bad conductor of heat and electricity.

-Melts at $11 9^{\circ} C$ .Its density is $1.96$ .

-It is stable above $95. 5^{\circ} C$ and below this changes into rhombic form. Hence, $95. 5^{\circ} C$ is the transition temperature.

$R h o mbi c S u lp h u r (α) b e l o w 95. 5^{\circ} ⇌ ab o v e 95. 5^{\circ} C M o n oc l ini c S u lp h u r (β)$

B)Amorphous form:

1)Plastic or $(γ - S u lp h u r)$ :

-It is prepared by plunging boiling sulphur into cold water.

-It is a supercooled liquid and does not have a sharp melting point.

-It consists of a long inverted zig-zag chain of sulphur atom.

-Insoluble in both $C S_{2}$ and Water.

2) Colloidal sulphur of $(δ - S u lp u r)$ :

-It is prepared by oxidation of $H_{2} S$ by oxidizing agents such as $co n c . H N O_{3}$ .

3)Milk of Sulphur:

-It is obtained by boiling sulphur and decomposing products formed with $H Cl$ .

-It is white solid.

-It is used in medicine.

Uses:

-Milk of sulphur is used in medicine.-Manufacturing of matches, gunpowder.-Used as disinfectant.-Vulcanization of rubber.

Compounds of $S u lp h u r :$

a) $H_{2} S :$

- Obtained by action of $d i l . H_{2} S O_{4}$ (non-oxidizing acids) on $F erro u s S u lp hi d e$ .

$F e S + d i l . H_{2} S O_{4} ⟶ H_{2} S + F e S O_{4}$

- It is purified by using MgO suspension in water.

- Moist $H_{2} S$ is dried by using $P_{2} O_{5}, N a_{2} S O_{4}$ .

Chemical Properties:

1) Combustion

- With excess it gives $S O_{2}$ .

- With Limited air it gives $S$ .

2) Acidic nature

- Weak and diprotic and dibasic acid.

3) Reducing action

-It reduces several oxidizing agent and gets oxidized to $S$ .

a) Halogen to haloacids. $(H X)$

b) $F e C l_{3}$ to $F e C l_{2}$

c) Acidified $K M n O_{4}$ to $M n S O_{4}$ and pink colour decolourizes.

d) Acidified $K_{2} C r_{2} O_{7}$ to $C r_{2} (S O_{4})_{3}$ and changes to green colour.

e) $S O_{2}$ to $S$ .

4) $H_{2} S$ as analytical agent ( Used to detect metal ions)

a) It can precipate $g r II$ metal ions such as $C u^{++}, H g^{++}$ as Sulphide in acidic, basic and neutral medium.

b) It can precipate $g r III B$ metal ions such as $Z n^{++}, C o^{++}$ in basic medium of $N H_{4} O H$ and $N H_{4} Cl$ .

Extra

-Bond angle : $92. 5^{\circ}$

-It is tested by using lead acetate $(C H_{3} COO)_{2} P b$ .

b) $S O_{2}$

Preparation

a) By burning Sulphur

$S + O_{2} ⟶ S O_{2}$

b) By roasting of sulphide ore.

$Z n S + O_{2} ⟶ 2 Z n O + 2 S O_{2}$

Lab preparation

-By action of $co n c . H_{2} S O_{4}$ on Copper.

$C u + co n c . H_{2} S O_{4} ⟶ C u S O_{4} + S O_{2} + H_{2} O$

Properties of $S O_{2}$

1)Acidic nature and is anhydride of $H_{2} S O_{3}$ .

$S O_{2} + H_{2} O ⟶ H_{2} S O_{3}$

2) Reducing action

It can reduce some oxidizing agents but self gets oxidized to $H_{2} S O_{4}$ .

3) Orange colour of acidified $K_{2} C r_{2} O_{7}$ is converted to green.

4) It can reduce neutral $K_{2} C r_{2} O_{7}$ to $C r_{2} (S O_{4})_{3}$ .

5) $S O_{2}$ is oxidized by following (to $H_{2} S O_{4}$ )

i) $K M n O_{4} / H^{+}$

ii) $K M n O_{4} / H_{2} O$

iii) $A l ka l in e K M n O_{4}$ .

6) It can reduce

i) $F e C l_{3}$ to $F e C l_{2}$

ii) $C u C l_{2}$ to $C u_{2} C l_{2}$

iii) $H g C l_{2}$ to $H g_{2} C l_{2}$

7)Halogen is reduced to haloacid

8) $S O_{2}$ as oxidizing agent :

i) $S O_{2} + H_{2} S ⟶ S + H_{2} O$

ii) $F e + S O_{2} ⟶ F e O + F e S$

9)Bleaching action of $S O_{2}$ is due to nascent Hydrogen $[H]$ .

$S O_{2} + H_{2} S O_{4} ⟶ H_{2} S O_{4} + [H] (S O_{2} g e t R e d u ce d)$

Uses:

-To manufacture $H_{2} S O_{4}$ .

-Used as bleaching agent for silk, wool, sugar solution.

-As germicide.

C) $S O_{3}$

Preparation

1) By dehydration of $co n c . H_{2} S O_{4}$

$H_{2} S O_{4} + P_{2} O_{5} ⟶ 2 H P O_{3} + S O_{3}$

2) By decomposition of $F e S O_{4}$ and $F e_{2} (S O_{4})_{3}$

$F e S O_{4} ⟶ F e_{2} O_{3} + S O_{3} + S O_{2}$

3) By Catalytic oxidation of $S O_{2}$ .

$S O_{2} + O_{2} ⟶ 2 S O_{3}$

Physical properties:

-It is colourless liquid and solidifies at $1 7^{\circ} C$ .

Chemical Properties

1) Acidic nature and anhydride of $H_{2} S O_{4}$ .

2) Decomposition

$S O_{3} ⟶ S O_{2} + O_{2}$

3) Oxidizing action

$S O_{3} + 2 H B r ⟶ S O_{2} + H_{2} O + B r_{2}$

4) With $co n c . H_{2} S O_{4}$ :

$S O_{3} + co n c . H_{2} S O_{4} ⟶ H_{2} S O_{2} O_{7}$

$H_{2} S O_{4}$ (Sulphuric Acid or Oil of Vitriol or Chamber acid)

-It is manufactured by contact process. Steps involved are :

a) Production of $S O_{2}$

b) Catalytic oxidation of $S O_{2}$ to $S O_{3}$

c) Conversion of $S O_{2}$ to Oleum by adding $co n c . H_{2} S O_{4}$ .

$S O_{2} + co n c . H_{2} S O_{4} ⟶ H_{2} S_{2} O_{7}$

d) Oleum is concerted to Sulphuric acid by adding calculated Water.

-In this manufacture , arsenic impurities is absorbed by $F e (O H)_{3}$ .

Physical Properties

-It is syrupy liquid and corrosive nature.

-It is diluted by adding acid to water not water to acid.

Chemical Properties

Acidic nature and dibasic or diprotic acid.
Decompose to give $S O_{2}$ .
It act as oxidizing agent as it produce nascent oxygen.
Dehydrating agent $(co n c . H_{2} S O_{4})$ :

a) Oxalic acid $(COO H)_{2}$ to $CO$ and $C O_{2}$ .

b) Formic acid $(H COO H)$ to $CO$ .

c) Alcohol to alkene

d) Carbohydrates $(C_{6} H_{1} 2 O_{6})$ to black mass of Carbon.

Uses:

It is used in manufacture of dyes, detergents, explosives, fertilizers.
Used in lead acid Cell.

$N a_{2} S_{2} O_{3} .5 H_{2} O$

Preparation

1) By boiling solution of $N a_{2} S_{2} O_{3}$ with Sulphur.

2) By boiling $N a O H$ and Sulphur.

Physical Properties

It is colourless crystalline solid soluble in water.

Uses:

As a fixer in photography.
Used in estimated of iodine.

Sulphur

Introduction

Properties:

Allotropes of Sulphur

A)Crystalline forms:

1) Rhombic or (α−Sulphur):

2) Monoclinic Sulphur or Prismatic or (β−Sulphur):

B)Amorphous form:

1)Plastic or (γ−Sulphur) :

2) Colloidal sulphur of (δ−Sulpur):

3)Milk of Sulphur:

Uses:

Compounds of Sulphur:

a) H2​S:

Chemical Properties:

b) SO2​

Preparation

Lab preparation

Properties of SO2​

Uses:

C)SO3​

Preparation

Physical properties:

Chemical Properties

H2​SO4​(Sulphuric Acid or Oil of Vitriol or Chamber acid)

Physical Properties

Chemical Properties

Uses:

Na2​S2​O3​.5H2​O

Preparation

Physical Properties

Uses:

1) Rhombic or $(α - S u lp h u r)$ :

2) Monoclinic Sulphur or Prismatic or $(β - S u lp h u r)$ :

1)Plastic or $(γ - S u lp h u r)$ :

2) Colloidal sulphur of $(δ - S u lp u r)$ :

Compounds of $S u lp h u r :$

a) $H_{2} S :$

b) $S O_{2}$

Properties of $S O_{2}$

C) $S O_{3}$

$H_{2} S O_{4}$ (Sulphuric Acid or Oil of Vitriol or Chamber acid)

$N a_{2} S_{2} O_{3} .5 H_{2} O$