DP Chemistry (first assessment 2025)

Question 23M.2.SL.TZ1.9a

Date	May 2023	Marks available	[Maximum mark: 7]	Reference code	23M.2.SL.TZ1.9a
Level	SL	Paper	2	Time zone	TZ1
Command term	Deduce, Explain, Outline, Suggest	Question number	a	Adapted from	N/A

[Maximum mark: 7]

23M.2.SL.TZ1.9a

(a)

The efficiency of a nuclear power plant is approximately 33 %.

(a.i)

Outline the meaning of the above statement in terms of energy conversion.

[1]

Markscheme

33 % of energy input/released «in fission» is converted to electricity ✓

Do not accept generalizations, such as “Only produces 33 % useful energy.”

(a.ii)

The fusion of two deuterium nuclei, ${}_{1}^{2}H$ , can occur in two ways:

${}_{1}^{2}H + {}_{1}^{2}H \to X + {}_{0}^{1}n$

${}_{1}^{2}H + {}_{1}^{2}H \to Y + {}_{1}^{1}p$

Deduce the nuclear symbols for X and Y using the correct notation.

X: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Y: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

[1]

Markscheme

X ${}_{2}^{3}H e$ AND Y ${}_{1}^{3}H$ ✓

(a.iii)

Explain which fusion reaction of deuterium releases more energy. Use section 36 of the data booklet.

[1]

Markscheme

2nd/Y/ ${}_{1}^{3}H$ AND formation ${}_{1}^{3}H$ has greater increase in binding energy «per nucleon than formation ${}_{2}^{3}H e$ ✓

Accept 2nd/Y/ ${}_{1}^{3}H$ AND “It is higher on the binding energy curve”.

(a.iv)

Suggest why the specific energy of deuterium in fusion is higher than that of uranium-235 in fission, yet the energy density of uranium is significantly greater than that of deuterium. Use section 1 of the data booklet.

[4]

Markscheme

deuterium contains more atoms per unit mass «than uranium as it has a lower molar mass» ✓

fusion releases more energy per atom than fission ✓

«solid» uranium «much» more dense «than deuterium»
OR
uranium contains more atoms per unit volume «than deuterium, as it is a solid» ✓

increase in density has a greater effect than fusion releasing more energy than fission ✓

Question 23M.2.SL.TZ1.9a

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