1/By drawing a table discuss by comparing and contrasting the physical propertie

ID: 533571 • Letter: 1

Question

1/By drawing a table discuss by comparing and contrasting the physical properties values of water,H2O and hydrogen sulphide,H2S in terms of their :

Boiling Points and Flash Points
Hydrogen Bonding
Vapor pressure (volatility)
Flammability
Toxicity to animals and humans

Hint: you may consult MSDS of each compound from Internet

2/ Starting from nitrobenzene , how can you prepare meta-dibromobenzene

3/ Write equations to show that Reduction of Ethyl propanoate with LiAlH4 gives two different alcohols.

4/ Thioethers and thioalcohols are structural isomers. Write the structures and give the names for two possible thioether and possible thioalcohol isomers of molecular formula, C4H10S

Explanation / Answer

Water vs Hydrogen sulphide

physical properties

Water (H2O)

Hydrogen sulphide (H2S)

Boiling Points

Oxygen is more electronegative than Sulphur and hence it can form more number of intermolecular H bonding with other water molecules, So its boiling point is high.

b. p.is 100 °C

H2S does not have hydrogen bond. It has weak Van der Waals forces of attraction keeping the molecules together, so it has lower boiling point.

b. p. is 60 °C

Flash Points

Water is a non-combustible substance, so it doesn't have a flash point.

H2S is combustible substance, so it has a flash point .Flash point is82.4 °C

Hydrogen Bonding

Oxygen is more electronegative than hydrogen; this gives the oxygen end of the water molecule a partial negative charge, while the hydrogen end has a partial positive charge. So Water is a polar molecule. And form hydrogen bonds.

Hydrogen bond is formed between hydrogen and any of the three electronegative atoms (N,O,F) covalently bonded to each other. There is no Hydrogen bond in H2S.

Vapor pressure (volatility

Less than H2S. 3.1690 kpa

1740 kPa (at 21 °C)

Flammability

Water is not flammable. Water is a waste product of combustion.

H2S is flammable.

Toxicity to animals and humans

It is vital for all known forms of life, so it is not toxic.

Gas is a highly toxic to animals and human.