Chemical Industry 1: Nitrogen Chemistry

Question 1

Be able to draw dot criss diagrams for nitrogen compounds:

N2, NH3, NH4+

Answer 1

Look at sheet

Question 2

What is special about bonding in NH4+

Answer 2

Dative Covalent bond between N and one of the H ( N donates 2 of its electrons to an H )

Question 3

NH3 = ?

Answer 3

AmmoniA

Question 4

NH4+ = ?

Answer 4

AmmoniUM

Question 5

Name 3 nitrogen oxides and give their formula

Answer 5

1. Nitrogen monoxide ( NO )
2. Dinitrogen monoxide ( N2 O)
3. Nitrogen dioxide ( NO2)

Question 6

What are other names for nitrogen monoxide ( NO )

Answer 6

• nitrogen ( II ) oxide

- nitric oxide

Question 7

Appearance of NO

Answer 7

Colourless gas

Question 8

Sources ( where does it come from ) of NO

Answer 8

1. Natural = lightening, forest fires, denitrifying bacteria
2. Human = combustion of fuels - driving vehicle / to generate electricity

( N2 + O2 combine in high heat of an engine )

Question 9

What are other names for dinitrogen monoxide ( N2O )

Answer 9

• nitrogen ( I ) oxide

- nitrous oxide

Question 10

Appearance of N2O

Answer 10

Colourless gas

Question 11

Sources ( where does it come from ) of N2O

Answer 11

• in soil by denitrifying bacteria

Question 12

What are other names for nitrogen dioxide( NO2 )

Answer 12

• nitrogen ( IV ) oxide

Question 13

Appearance of NO2

Answer 13

Brown gas

Question 14

Sources ( where does it come from ) of NO2

Answer 14

• oxidation of NO in air

Question 15

Write balanced equation for formation of nitrogen ( II ) oxide

Answer 15

N2 (g) + O2 (g) —> 2NO (g)

Question 16

Write balanced equation for conversion of nitrogen ( II ) oxide to nitrogen ( IV ) oxide

Answer 16

2 NO(g) + O2(g) —> 2 NO2(g)

Question 17

Be able to draw dot and Ross diagrams of the nitrate ions

• nitrate ( V ) ion ( NO3- )
• nitrate ( III ) ion ( NO2- )

Answer 17

Look at sheet

Question 18

What is the solubility of nitrate ions like

Answer 18

Both nitrate ions are VERY SOLUBLE in water

Question 19

NO3- = ?

Answer 19

Nitrate ( V ) ion

because oxidation of N = +5

Question 20

NO2- =?

Answer 20

Nitrate ( III ) ion

because oxidation state of N = +3

Question 21

5 stages of nitrogen cycle

Answer 21

1. Nitrogen Fixation
2. Absorption by plants
3. Moving along food chains
4. Death of organisms
5. Dentrification

Question 22

Explain 1st stage of nitrogen cycle - Nitrogen fixation

Answer 22

nitrogen in atmosphere to unreactive to be used directly has to be changed into soluble ions

nitrogen fixing bacteria in roots nodules of legumes will convert nitrogen into nitrate

lightening converts nitrogen into nitrates

Haber process will convert nitrogen into ammonia & nitrifying bacteria will turn ammonia into nitrates

Question 23

Explain 2nd stage of nitrogen cycle - Absorption by plants

Answer 23

plants will absorb nitrates through roots by active transport

Question 24

Explain 3rd stage of nitrogen cycle - moving along food chain

Answer 24

animals will eat plants and nitrogen from plants protein will become protein in animal

nitrogen is also passed from one animal to another by feeding

Question 25

Explain 4th stage of nitrogen cycle - death of organisms

Answer 25

decomposers ( bacteria and fungi ) will break down urea, egested material and dead bodies & nitrogen compounds will be returned to the soil as ammonium ions

nitrifying bacteria will convert ammonia ions into nitrates for plants to absorb

Question 26

Explain 5th stage of nitrogen cycle- Denitrification

Answer 26

denitrifying bacteria in the soil will break down nitrates and return nitrogen gas into the air

occurs in waterlogged soil so can be prevented by reducing drainage

Question 27

Name 5 conversions within the nitrogen cycle

Answer 27

1. Nitrification= NO2- —> NO3-
2. Denitrification= NO3- —> N2
3. Putrefaction= NH4+ —> NH3
4. Ammonia Synthesis= N2- —> NH3
5. In atmosphere= NO —> NO2

Question 28

Describe 6 steps of nitrogen cycle in terms of how nitrogen compounds formed/ converted one after the other

Answer 28

1. Nitrogen gas ( N2 ) —> AmmoniA ( NH3 )
2. AmmoniA ( NH3 ) —> Ammonium ions ( NH4+ )
3. Ammonium ( NH4+ ) —>
   Nitrites/ Nitrate ( III ) ions ( NO2-)
4. Nitrites/ nitrate ( III ) ions ( NO2- ) —> NitrAtes / nitrate ( V ) ions ( NO3-)
5. NitrAtes/ nitrate ( V ) ions ( NO3-) —> Nitrogen ( N2 in atmosphere)
6. Nitrogen gas ( N2) —> nitrogen oxides ( NO, NO2, N2O )

Question 29

Write an equation of the formation of nitrate ( III ) ion from an ammonium ion

Answer 29

NH4+ + 1.5 O2 —> NO2- + 2 H+ + H20

Question 30

Write an equation of the formation of the nitrate ( V ) ion from nitrate ( II ) ion

Answer 30

NO2- + 0.5 O2 —> NO3-

Question 31

Describe test for nitrate ( V ) ion ( NO3- )

Answer 31

1. Warm solution with sodium hydroxide ( NaOH )
2. Add aluminium foil
3. ( in presence alkali ) aluminium reduces nitrate ion to produce ammonia gas
4. Ammonia gas = damp red litmus —> blue

Question 32

Describe test for ammonium ion ( NH4+ )

Answer 32

1. Add sodium hydroxide ( NaOH )
2. Heat gently
3. Ammonia ( NH3 ) has produced = turn red damp litmus paper blue

Question 33

Equation of ammonium ion to ammonia gas in presence of alkali

Answer 33

NH4+ (aq) + OH- (aq) —> NH3(g) + H2O (l)

Question 34

Describe the bonding in nitrogen

Answer 34

Triple bond in N atoms requires a lot of energy to break