Ch2 Sulphur

Hydrogen Sulphide (H2S)

A colorless gas with a repulsive smell similar to rotten eggs, it is extremely poisonous and can be lethal even at low concentrations. Exposure to H2S can cause irritation of the eyes, nose, and throat, and prolonged exposure can lead to respiratory failure and death. It is produced naturally in volcanic gases, anaerobic decay, and certain industrial processes.

Preparation of H2S

Can be prepared by the action of a dilute acid on a metallic sulphide.

Kipp’s Apparatus

An apparatus that allows for the supply of gases like H2S and CO2 as needed.

Relative density of H2S

H2S is about 1.18 times denser than air.

Physical properties of H2S

Colorless, poisonous, moderately soluble in water, turns blue litmus paper red.

Chemical properties of H2S

Can react with oxygen, behaving as a reducing agent and exhibiting various reactions.

Reducing agent

A substance that donates electrons in a chemical reaction, H2S is a strong reducing agent.

Reaction of H2S with oxygen

Burns with a pale blue flame to produce SO2 and H2O in a plentiful supply of air.

Formation of yellow solid from H2S

Occurs when the supply of oxygen is limited in its reaction with oxygen.

Silver tarnishing agent

H2S tarnishes silver due to its sulfur content.

Acid-base reaction of H2S

H2S behaves as a weak dibasic acid, slightly ionizing in water.

Precipitating agent of H2S

Forms metallic sulphides, typically black solids that are insoluble in water.

Sulphur Dioxide (SO2) preparation

Can be prepared by heating sodium sulphate (IV) with hydrochloric acid.

Physical properties of SO2

Colorless, poisonous gas with an irritating smell, soluble in water.

Chemical properties of SO2

Acts as both a reducing and oxidizing agent, can form acids.

Bleaching agent properties of SO2

SO2 is a good bleaching agent due to its reducing power.

Contact process

An industrial method to manufacture concentrated sulphuric acid.

Concentrated Sulphuric Acid (H2SO4)

Colorless, odorless oily liquid with a high boiling point, highly corrosive.

Diprotic acid

H2SO4 is a strong diprotic acid, capable of donating two protons.

Oxidizing agent properties of H2SO4

Can be reduced to SO2 during redox reactions.

Dehydrating agent properties of H2SO4

Removes water and can dehydrate substances like sugar and crystals.

Common Sulphates (VI)

Include ammonium sulphate, potassium sulphate, and calcium sulphate.

Test for Sulphate (IV)

If SO2 gas is evolved upon reacting with a dilute acid, then sulphate (IV) is present.

Test for Sulphate (VI)

A white precipitate of BaSO4 indicates the presence of sulphate (VI).

Reaction with hydrogen sulphide (H2S)

H2S can react with concentrated H2SO4, reducing it to SO2.

Barium sulphate (BaSO4)

A white precipitate formed when barium chloride is added to a solution containing sulphate (VI).

Use of H2SO4 in fertilizers

Production of fertilizers like (NH4)2SO4 and Ca(H2PO4)2.

H2SO3 formation from SO2

SO2 dissolves in water to form the dibasic weak acid H2SO3.

Oxidation states in reactions

Understanding oxidation states is crucial for predicting reaction outcomes of H2O, SO2, etc.

Hydration of sulphuric acid

H2SO4 reacts strongly with water, producing heat.

Concentration effect on acids

Concentrated H2SO4 can act as a dehydrating agent on organic compounds.

Chemical properties of SO2 as a reducing agent

SO2 is a strong reducing agent, easily reacting with oxidizing agents.

Sodium sulphate (Na2SO4) thermal stability

Stable to heat compared to other sulphates that decompose.