Chapter 12. Nitrogen And Sulfur

Question 1

Why is nitrogen chemically inert?

Answer 1

-Triple bond of 944kJmol^-1
-non-polar as both atoms in the molecule are the same

Question 2

Note

Answer 2

Ammonia has a tryangular pyramid shape with 107 bond angles
-Ammonia can form positive ions like metal ions, ammonium
-NH₃ + HCl <–> NH₄⁺ + Cl^-
-Ammonia can be displaced from its salts by reaction with a base
-NH₄NO₃ + NaOH –> NaNO_{3</sub + NH3 + H2O}

Question 3

Nitrogen oxides

Answer 3

At high temperatures and with a spark, nitrogen will reaction with oxygen to form nitrogen monoxide
-This occurs naturally during thunderstorms and in combustion engines
-N₂ + O₂ –> 2NO
-Further oxidation of NO by oxygen in air leads to NO₂

Question 4

What are the downsides of NO_x(mixture of nitrogen oxides) pollutants?

Answer 4

-It reacts in moist air(oxygen and water) to form nitric acid- a componet of acid rain
-It can cause breathing problems such as asthma
-It contributes to photochemical smogs when it reacts with unburnt hydrocarbons from fuels.

Question 5

How does a catalytic converter work?

Answer 5

Platinum and rhodium in the catalytic converter catalyse the following reactions
-carbon monoxide + nitrogen oxides –> carbon dioxide + nitrogen
-hydrocarbons + nitrogen oxides –> carbon dioxide + nitrogen + water
-CO + NO –> CO₂ + 0.5N₂
-2CO + NO₂ –> 2CO₂ + 0.5N₂
-C₈H₁₈ + 25NO –> 8CO₂ + 9H₂O + 12.5N₂
-C₈H₁₈ + 25NO₂ –> 16CO₂ + 18H₂O + 12.5N₂

Question 6

Note

Answer 6

PANs – peroxyacetyl nitrates
-Genral formula –> R-CO-OONO₂
-Photochemical smogs are lachrymators - they cause eye irritation
-Photochemical smogs also cause breathing and heart problems

Question 7

Sulfur

Answer 7

Many fossil fuels contain sulfur, when burnt they create sulfur dioxide which reacts with oxygen and water to form sulfuric acid, a component of acid rain, the reaction is catalysed by NO_x
-S_s + O_2(g) – SO_2(g) - when fuel is burnt
-2SO_2(g) + O_2(g) –> 2SO_3(g) - in the atmsophere due to NO_x
-2NO + O₂ –> 2NO₂
-SO₂ + NO₂ –> SO₃ + NO
-SO₃ + H₂O –> H₂SO₄