nitrogen and sulfur Flashcards
Why is nitrogen very unreactive?
● Nitrogen exists as a diatomic molecule whereby 2
nitrogen atoms are joined by a triple bond (N≡N).
● The enthalpy of this bond is very high and hence
requires a lot of energy to break.
● There isn’t a permanent dipole in the molecule so it is
fairly resistant to electrophilic and nucleophilic attack.
How does ammonia act as a base?
Ammonia (NH3) is a weak base because there
is a lone pair of electrons on the nitrogen
atom that allow the molecule to accept a
+
proton, forming an ammonium ion, NH4 .
Describe the bonding and structure of ammonia
There are 3 bonding pairs of electrons (N-H covalent bonds). In addition to this, there is 1 lone pair of electron. The shape is pyramidal and it has a 107° bond angle.
Describe the bonding and structure of ammonium
ions
- 4 bonding pairs, no lone pairs. - One dative covalent bond. - Tetrahedral shape and bond angle of 109.5°.
How is an ammonium ion formed during the reaction
between hydrochloric acid and ammonia?
Full equation: NH3(aq) + HCl(aq) → NH4Cl(aq)
+ +
Ionic equation: NH3(aq) + H (aq) → NH4 (aq)
Ammonia accepts a proton from the acid to form
an ammonium ion.
What can be used to displace ammonia from its
salts? What is formed during this reaction?
When an alkali is reacted with an
ammonium salt, ammonia is displaced.
This reaction also forms a salt and water.
Write an equation for the reaction of ammonium
chloride with sodium hydroxide
NH4Cl(s) + NaOH(aq) → NH3(g) + H2O(l) + NaCl(aq)
Name the following compounds: N2O, NO and NO2
N2O = Nitrous oxide
NO = Nitric oxide
NO2 = Nitrogen dioxide
State the colours of the following gases:N2O, NO and NO2
N2O = colourless
NO = colourless
NO2 = reddish-brown
How are oxides of nitrogen produced
naturally?
By lightning:
N2 + O2 → 2NO
NO + ½O2 → NO2
Alternatively, microbes in the soil produce nitrous oxide (N2O)
- -
nitrate ions (NO3 ), nitrite ions (NO2 ) and other
nitrogen-containing compounds.
How are oxides of nitrogen produced by human
activity?
● Made from fossil fuel combustion.
● Formed in nitric acid manufacture.
● NO made as a result of the high pressures and
temperatures of car engines: N2 + O2 → 2NO.
Describe how catalytic converters work
Nitrogen monoxide is formed in car engines:
N2(g) + O2(g) → 2NO(g) A catalytic converter is made up of a ceramic honeycomb structure coated in a thin layer of metal catalysts (such as platinum and rhodium). The catalytic converter removes a majority of NO so that it isn’t released into the atmosphere:
2NO(g) + 2CO(g) → N2(g) + CO2(g)
Why are atmospheric oxides of nitrogen pollutants?
● Oxides of nitrogen can react with oxygen and water in
the clouds to produce nitric acids (acid rain).
● Nitrogen monoxide can catalyse the oxidation of SO2,
causing acid rain.
● Nitrogen dioxide can contribute to photochemical smog.
How does nitrogen dioxide catalyse the oxidation of
atmospheric sulfur dioxide?
Nitrogen dioxide catalyses the conversion of SO2 into SO3:
NO2(g) + SO2(g) → SO3(g) + NO(g) Nitrogen monoxide reacts with oxygen to reform the catalyst:
2NO(g) + O2(g) → 2NO2(g)
How does the combustion of sulfur-contaminated
fossil fuels lead to the formation of atmospheric
sulfur dioxide?
Fossil fuels (such as coal and oil) contain small
amounts of sulfurous compounds.
Sulfur dioxide is released when these
compounds undergo combustion.
