DP Chemistry (first assessment 2025)

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Question 23M.2.HL.TZ1.3a

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Date May 2023 Marks available [Maximum mark: 6] Reference code 23M.2.HL.TZ1.3a
Level HL Paper 2 Time zone TZ1
Command term Calculate, Explain, Outline, Suggest, Write Question number a Adapted from N/A
a.
[Maximum mark: 6]
23M.2.HL.TZ1.3a
(a)

High-pressure carbon monoxide disproportionation (HiPco) produces carbon atoms that react with nano catalysts to produce carbon nanotubes.

(a.i)

Write the equation for the disproportionation of carbon monoxide to produce carbon atoms.

[1]

Markscheme

2CO(g) → C(s) + CO2(g) ✓


Accept reversible arrows.

(a.ii)

Calculate the percent atom economy of producing carbon using this method. Use section 1 of the data booklet.

[1]

Markscheme

«100 × 12.01 / 2 × (12.01+16.00) = » 21.44 % ✓

(a.iii)

Outline how a metal functions as a heterogeneous catalyst.

[2]

Markscheme

«gaseous» reactants adsorb onto «metal» surface
OR
catalyst provides surface for reaction to occur ✓

weakens «reactant» bonds
OR
products desorb ✓


Accept lowers activation energy for M2.

(a.iv)

Explain whether the production of carbon nanotubes using HiPco is a bottom up or top down nanotechnology technique.

[1]

Markscheme

bottom up AND molecular assembly «rather than decomposition» ✓

(a.v)

Suggest one health risk of using nanoparticles.

[1]

Markscheme

Any one of:

more easily airborne/inhaled ✓

have similar dimensions as biological molecules/interfere with biochemical reactions ✓

easily absorbed into body ✓

may cross cell membranes ✓

large surface area could increase toxicity ✓

human defence system not effective with small size ✓

 

Do not accept just large surface area OR toxic/increased toxicity.