DP Chemistry (first assessment 2025)

Question 23M.2.HL.TZ1.12a

Date	May 2023	Marks available	[Maximum mark: 12]	Reference code	23M.2.HL.TZ1.12a
Level	HL	Paper	2	Time zone	TZ1
Command term	Deduce, Determine, Explain, Outline, Suggest	Question number	a	Adapted from	N/A

[Maximum mark: 12]

23M.2.HL.TZ1.12a

(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)

The mass of deuteron, the nucleus of a deuterium atom, is 2.013553 amu. Determine the binding energy, in J, of deuteron. Use sections 2 and 4 of the data booklet and 1 amu = 1.660540 × 10⁻²⁷ kg.

^{[Source: NIST, n.d. Deuteron mass in u. [online]
Available at: https://physics.nist.gov/cgi-bin/cuu/Value?mdu#mid}
^{[Accessed 20 May 2021].]}

[3]

Markscheme

m(deuteron) = 2.013553 «amu» × 1.660540 × 10^–27 «kg amu^–1=»
OR
3.343585 × 10⁻²⁷ «kg» ✓

«Δm = (mass of reactants − mass of products)»
Δm = «(1.672622 × 10⁻²⁷ kg + 1.674927 × 10⁻²⁷ kg) − 3.343585 × 10⁻²⁷ kg =» 3.964 × 10⁻³⁰ «kg» ✓

E = «mc² = 3.964 × 10⁻³⁰ kg × (3.00 × 108 m s⁻¹)² =» 3.568 × 10⁻¹³ «J» ✓

Award [3] for correct final answer.

(a.v)

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 ✓

(a.vi)

Uranium needs to be enriched from its natural isotope, ${}^{238}U$ , to the more fissile ${}^{235}U$ for use in nuclear reactors. Explain how the proportion of ${}^{235}U$ in natural uranium is increased.

[2]

Markscheme

uranium converted to uranium hexafluoride/UF6 «gas» ✔

centrifuge
OR
lower mass isotope/ ${}^{235}U$ effuses/diffuses more rapidly
OR
higher mass isotope/ ${}^{235}U$ moves/closer to outside of centrifuge
OR
lower mass isotope/ ${}^{235}U$ stays in/removed from middle of centrifuge ✔

Question 23M.2.HL.TZ1.12a

Select a Test

Confirm action