Nitrogen And Sulfur

Question 1

Why is N2 gas so unreactive

Answer 1

N-N triple bond is very strong high Ea required

Non polar

Question 2

How is S present in environment

Answer 2

In form of ZnS
In fossil fuels, coal
And volcanoes

Question 3

How is SO2 formed in the atmosphere

Answer 3

S (fossil fuel/volcano) + O2(g) —> SO2 (g)

Question 4

How is acid rain formed

Answer 4

Extreme temp in car engine or lightning strikes
N2 + O2—> NO or NO2 (O.A)
SO2 (R.A)
NO2 acts as a catalyst

NO2 + SO2—-> SO3 + NO
NO + 1/2 O2—–> NO2

SO3 + H2O (in clouds)—> H2SO4
2NO2 + H2O + O2 —-> HNO3 + HNO2

Question 5

Effects of acid rain

Answer 5

• Corrosion of limestone building/metal structures
• Damage to vegetation
• Soil and water bodies become acidic
• Skin/eye irritation

Question 6

How are acidic soils neutralised

Answer 6

Addition of lime (Ca(OH)2) / limestone (CaCO3)

Ca(OH)2 + 2H+ —-> Ca2+ + 2H2O
CaCO3 + 2H+ —-> Ca2+ + 2H2O + CO2

Question 7

Show the displacement reaction of NH3 from ammonium salts when lime and fertiliser is added together

Answer 7

Ca(OH)2 + (NH4)2SO4—> CaSO4 + H2O + NH3 (released from soil)

Question 8

How are industrial gases neutralised

Answer 8

SO2/NO2- industrial gases

SO2/NO2 + CaCO3/Ca(OH)2 ----> CaSO3
                                                               Or Ca(NO3)2 or Ca(NO2)2

Question 9

Describe the Habers process

Answer 9

N2 + 3H2 <====> 2NH3 (ΔH= -92 Kjmol-1)

Fe/Fe2O3 - catalyst
450°C temperature
200 atm pressure

N2- fractional distilation of liquified air
H2-cracking of oil/electrolysis of H2O

NH3 is removed -reaction shifts forward
High pressure - high economic cost
Low temp- reduces rate of reaction

Question 10

Uses of NH3

Answer 10

1) fertilisers - ammonium salts
2) manufacture of nitric acids
3) explosives, detergents dyes

Question 11

What are the conditions for contacts process

Answer 11

V2O5- catalyst
Pressure - 1-3atm
Temperature 450°C

Question 12

Describe reactions of the contacts process

Answer 12

S + O2 —–> SO2
2SO2 + O2<===> 2SO3

SO3 + conc. H2SO4—> H2S2O4 (oleum)
H2S2O4 + H2O —> 2H2SO4

Question 13

Uses of H2SO4 from contacts process

Answer 13

Car batteries
Paints
Fertiliser

Question 14

How do nitrates reach soil

Answer 14

1) acid rain
N2 + O2 —> NO or NO2
NO + 1/2 O2—-> NO2
2NO2 + H2O + 1/2 O2 —-> 2HNO3

2) fertiliser

Question 15

Why is excess fertiliser harmful

Answer 15

Washes away into rivers/lakes
Promotes algae growth
Algae blocks sunlight destroys marine plants
Bacteria mtiplies because of dead plants and consume oxygen
Marine life dead

Question 16

Why is NH3 basic

Answer 16

Forms dative bond with H+ ion and forms ammonium salts

Question 16

Why is NH3 basic

Answer 16

Forms dative bond with H+ ion and forms ammonium salts

Question 17

Name the following compounds N2O NO NO2

Answer 17

N2O = nitrous oxide
NO = nitric oxide
NO2 = Nitrogen dioxide

Question 18

State the colour of NO and NO2

Answer 18

NO colourless

NO2 brown

Question 19

Describe how catalytic converters work

Answer 19

Pd/Pt/Rh catalysts

2NO + 2CO —> N2 + CO2

Question 20

Ammonia is a weak base

What is meant by this term

Answer 20

Proton acceptor
Partially ionises in water
NH3 + H+ <=> NH4+

Question 21

Why does calcium hydroxide react with ammonium compounds to form ammonia

Answer 21

Displaces NH3

Question 22

Sulfur dioxide is used as food preservative. What property of sulfur dioxide enables it to act this way

Answer 22

Antioxident r.a

Kills bacteria

Question 23

How does NO2 form in factories

Answer 23

Combustion provides large amount of heat for breakage of strong N-N bond triple

N2 and oxygen ‘in atmosphere’ react to form NO2