Green Chemistry & Sustainability
Level: 1 (Recognition) Time Limit: 20 minutes Total Marks: 30
Section A — Multiple Choice (1 mark each) — 10 marks
Q1. Which of the following best defines atom economy?
- (a) The cost of atoms used in a reaction
- (b) The percentage of reactant atoms that end up in the desired product
- (c) The number of atoms in the smallest molecule
- (d) The energy required per mole of atoms
Q2. How many principles of green chemistry are there (Anastas & Warner)?
- (a) 6 (b) 10 (c) 12 (d) 15
Q3. Which principle states it is better to prevent waste than to treat or clean it up after it is formed?
- (a) Principle 1 (b) Principle 5 (c) Principle 9 (d) Principle 12
Q4. Supercritical CO₂ is considered a green solvent mainly because it is:
- (a) Highly toxic but cheap
- (b) Non-flammable, non-toxic, and easily removed by depressurisation
- (c) A strong oxidising acid
- (d) Only usable below 0 °C
Q5. The green monopropellant LMP-103S is based on:
- (a) Hydrazine
- (b) Ammonium dinitramide (ADN)
- (c) Hydroxylammonium nitrate (HAN)
- (d) Liquid oxygen
Q6. Which propellant is the AFRL green alternative based on HAN?
- (a) LMP-103S (b) AF-M315E (c) MMH (d) UDMH
Q7. In water electrolysis for the hydrogen economy, hydrogen gas is produced at the:
- (a) Anode (oxidation)
- (b) Cathode (reduction)
- (c) Salt bridge
- (d) Reference electrode
Q8. A hydrogen–oxygen fuel cell produces which by-product?
- (a) CO₂ (b) NOₓ (c) Water (d) SO₂
Q9. Which solvent property makes ionic liquids attractive for green chemistry?
- (a) High vapour pressure
- (b) Negligible vapour pressure (low VOC emission)
- (c) Extreme flammability
- (d) They boil below room temperature
Q10. Carbon capture and storage (CCS) primarily targets which greenhouse gas?
- (a) CH₄ (b) CO₂ (c) N₂O (d) O₃
Section B — Matching (1 mark each) — 6 marks
Q11. Match each green-chemistry term (i–vi) to its correct description (A–F).
| Term | Description |
|---|---|
| (i) Atom economy | (A) Uses renewable rather than depleting feedstocks |
| (ii) Catalysis | (B) Fraction of reactant mass appearing in product |
| (iii) Renewable feedstock | (C) Preferred over stoichiometric reagents (Principle 9) |
| (iv) Supercritical CO₂ | (D) Green propellant based on ADN |
| (v) LMP-103S | (E) Solvent removed simply by releasing pressure |
| (vi) Fuel cell | (F) Converts chemical energy to electricity with H₂O output |
Section C — True / False with justification (2 marks each) — 14 marks
(1 mark for correct T/F, 1 mark for correct justification)
Q12. A reaction with 100% atom economy produces no by-products. (T/F + justify)
Q13. Hydrazine is preferred over green propellants because it is completely non-toxic. (T/F + justify)
Q14. Water is always the greenest solvent choice for every organic reaction. (T/F + justify)
Q15. Green hydrogen is produced by electrolysis powered by renewable electricity. (T/F + justify)
Q16. A high percentage yield always guarantees a high atom economy. (T/F + justify)
Q17. Ionic liquids emit large amounts of volatile organic compounds (VOCs) into the atmosphere. (T/F + justify)
Q18. Green chemistry Principle of "designing safer chemicals" aims to reduce toxicity while preserving function. (T/F + justify)
Answer keyMark scheme & solutions
Section A (10 marks)
Q1 — (b) [1] Atom economy = fraction of reactant atoms incorporated into the desired product; it measures intrinsic efficiency, not cost or energy.
Q2 — (c) 12 [1] Anastas & Warner formulated the 12 principles (1998).
Q3 — (a) Principle 1 [1] "Prevention" — waste prevention beats end-of-pipe treatment.
Q4 — (b) [1] scCO₂ is non-toxic, non-flammable, abundant, and simply vents off on depressurisation, leaving no solvent residue.
Q5 — (b) ADN [1] LMP-103S (ECAPS) is an ammonium dinitramide-based blend.
Q6 — (b) AF-M315E [1] The AFRL propellant is HAN-based (hydroxylammonium nitrate).
Q7 — (b) Cathode [1] Reduction: occurs at the cathode; O₂ forms at the anode.
Q8 — (c) Water [1] Overall: , the only product.
Q9 — (b) [1] Their negligible vapour pressure means they don't evaporate → low air pollution / VOC.
Q10 — (b) CO₂ [1] CCS captures anthropogenic carbon dioxide.
Section B (6 marks) — 1 mark each
| Term | Answer |
|---|---|
| (i) Atom economy | B |
| (ii) Catalysis | C |
| (iii) Renewable feedstock | A |
| (iv) Supercritical CO₂ | E |
| (v) LMP-103S | D |
| (vi) Fuel cell | F |
Section C (14 marks)
Q12 — TRUE [1] Justification [1]: If atom economy is 100%, every atom of the reactants is incorporated into the desired product, so nothing is left over as by-product (e.g. addition/rearrangement reactions).
Q13 — FALSE [1] Justification [1]: Hydrazine is highly toxic and carcinogenic; green propellants (LMP-103S, AF-M315E) were developed precisely to replace it because it is dangerous, not because it is safe.
Q14 — FALSE [1] Justification [1]: Water is green only when reactants/products are compatible (soluble, water-stable). Many organic reactions require anhydrous conditions or water-sensitive reagents, so water is not universally suitable.
Q15 — TRUE [1] Justification [1]: "Green" hydrogen is defined by electrolysis of water using renewable (solar/wind) electricity, giving essentially zero-carbon H₂.
Q16 — FALSE [1] Justification [1]: Yield measures how much product is obtained relative to theoretical; atom economy measures how many reactant atoms are inherently retained. A reaction can give 100% yield yet low atom economy if it produces large by-product molecules (e.g. Wittig, substitution).
Q17 — FALSE [1] Justification [1]: Ionic liquids have negligible vapour pressure, so they do not evaporate to release VOCs — this is a key green advantage.
Q18 — TRUE [1] Justification [1]: Principle 4 ("Design safer chemicals") aims to minimise toxicity while retaining desired efficacy/function.
[
{"claim": "Atom economy of addition reaction with single product is 100%", "code": "product_mass=100; reactant_mass=100; ae=Rational(product_mass,reactant_mass)*100; result=(ae==100)"},
{"claim": "H2O2 (green oxidant) decomposition water balance: 2H2O2 -> 2H2O + O2 conserves H and O", "code": "H_left=2*2; H_right=2*2; O_left=2*2; O_right=2*1+2; result=(H_left==H_right and O_left==O_right)"},
{"claim": "Fuel cell reaction 2H2 + O2 -> 2H2O balances atoms", "code": "H_left=2*2; H_right=2*2; O_left=2; O_right=2*1; result=(H_left==H_right and O_left==O_right)"},
{"claim": "There are 12 principles of green chemistry", "code": "n=12; result=(n==12)"}
]