AS Level Chemistry chapter 12: Nitrogen and sulfur MCQs with answers
By Team Megalecture · Updated 4 Nov 2026
22 exam-style questions on Nitrogen and sulfur, each with the answer and a short explanation. Ten of them are below to try. The chapter test draws ten fresh questions each time and is marked the moment you finish, with your score by topic.
Try each one, then open the answer. These ten stay the same; the test draws new ones every time.
1. Which statements about oxides of nitrogen are correct? 1 nitrogen monoxide is formed naturally during lightning storms 2 nitrogen monoxide forms in petrol engines because petrol contains nitrogen compounds 3 in a catalytic converter nitrogen monoxide is reduced to nitrogen
A
1, 2 and 3
B
1 and 2 only
C
2 and 3 only
D
1 and 3 only
Show answer
Answer: D. Lightning and hot engines both supply enough energy for N2 and O2 from the air to combine; the nitrogen does not come from the fuel, so statement 2 is wrong. NO (N +2) is reduced to N2 (N 0) in the converter.
2. Ammonia reacts with a hydrogen ion to form the ammonium ion. Which statement about NH4+ is correct?
A
the dative N–H bond is longer than the other three
B
the nitrogen atom still has one lone pair
C
the ion contains 11 electrons
D
all four N–H bonds are identical once the ion has formed
Show answer
Answer: D. The lone pair on N forms a dative bond to H+, but once formed it cannot be told apart from the other three. The ion has 11 protons but 10 electrons, and no lone pair remains.
3. Which metals are commonly used as the catalyst in the catalytic converter of a petrol car?
A
iron and molybdenum
B
copper and zinc
C
nickel only
D
platinum and rhodium
Show answer
Answer: D. Platinum, palladium and rhodium coated on a ceramic honeycomb catalyse the removal of NO, CO and unburned hydrocarbons. Iron is the Haber process catalyst.
4. Ammonia is released when an ammonium salt is warmed with alkali: NH4+ + OH− → NH3 + H2O. Which statement about this reaction is correct?
A
NH4+ is a proton donor and OH− is a proton acceptor
B
NH4+ is a proton acceptor and OH− is a proton donor
C
nitrogen is reduced from +3 to −3
D
it is a displacement in which a more reactive metal replaces ammonium
Show answer
Answer: A. OH− is a stronger base than NH3, so it removes H+ from NH4+. Nitrogen is −3 throughout, so it is acid–base, not redox.
5. Peroxyacetyl nitrate (PAN), a component of photochemical smog, is formed from
A
nitrogen oxides and unburned hydrocarbons in sunlight
B
sulfur dioxide and water vapour
C
carbon monoxide and ozone
D
ammonia and nitric acid
Show answer
Answer: A. NO and NO2 from vehicle exhausts react with unburned hydrocarbons under the action of sunlight to produce PAN, an eye and lung irritant found in smog over cities.
6. Use these bond energies to find ΔH for N2(g) + O2(g) → 2NO(g): N≡N 945 kJ mol−1, O=O 498 kJ mol−1, the bond in NO 631 kJ mol−1.
A
−181 kJ mol−1
B
+181 kJ mol−1
C
+812 kJ mol−1
D
+1443 kJ mol−1
Show answer
Answer: B. Bonds broken 945 + 498 = 1443; bonds made 2 × 631 = 1262; ΔH = 1443 − 1262 = +181 kJ mol−1. The large energy needed to break N≡N is why N2 and O2 react only at very high temperatures. +812 counts only one NO bond.
7. Which reagent, when warmed with solid ammonium chloride, releases ammonia gas?
A
dilute hydrochloric acid
B
aqueous silver nitrate
C
water
D
aqueous sodium hydroxide
Show answer
Answer: D. OH− is a stronger base than NH3, so it removes the proton from NH4+: NH4+ + OH− → NH3 + H2O. The ammonia turns damp red litmus blue.
8. Why is nitrogen gas so unreactive?
A
the N≡N triple bond is very strong and the molecule is non-polar, so there is no partial charge to attract reactants
B
nitrogen atoms are very small
C
nitrogen has a full outer shell of electrons
D
nitrogen molecules are very light
Show answer
Answer: A. Breaking the triple bond needs about 945 kJ mol−1, and because the two atoms are identical there is no dipole to start a reaction. Nitrogen atoms do not have a full outer shell; the molecule does.
9. Which equation shows how nitrogen monoxide is removed in a catalytic converter?
A
N2 + O2 → 2NO
B
2NO + O2 → 2NO2
C
NO2 + SO2 → NO + SO3
D
2NO + 2CO → N2 + 2CO2
Show answer
Answer: D. On the platinum/rhodium catalyst, NO oxidises CO while itself being reduced to harmless nitrogen. The first equation is how NO forms in the hot engine; the others are atmospheric reactions.
10. Ammonium sulfate is warmed with excess aqueous sodium hydroxide: (NH4)2SO4 + 2NaOH → Na2SO4 + 2NH3 + 2H2O. What volume of ammonia at room conditions is released from 0.0100 mol of ammonium sulfate?
A
0.120 dm3
B
0.240 dm3
C
0.960 dm3
D
0.480 dm3
Show answer
Answer: D. Each formula unit contains two NH4+ ions, so 0.0100 mol gives 0.0200 mol of NH3. Volume = 0.0200 × 24.0 = 0.480 dm3.
22, each with the answer and a short explanation, across 1 topics: Nitrogen and sulfur. Every chapter test draws ten of them, so you can take it many times.
Is the AS Level Chemistry chapter 12 test free?
Yes. The test, the answers and the explanations are free and need no sign-up. Sign in only if you want your scores kept across devices.
How is the chapter test marked?
The moment you press Finish: your score, the right answer and an explanation for every question, and the ones you got wrong saved in My mistakes to retry.
