MC test: Nuclear fusion & nuclear fission (HL)

Multiple choice test on C.7 Nuclear fusion & nuclear fission (HL)

Use the following 'quiz' to test your knowledge and understanding of this sub-topic. As this relates to a sub-topic on the options you may need access to the IB data booklet.

If you get an answer wrong, read through the explanation carefully to learn from your mistakes.

Which are correct statements about nuclear binding energy?

I. It is the energy required to separate a nucleus into its constituent neutrons and protons.

II. It is equal to the mass defect between the constituent nucleons and the actual mass of the nucleus.

III. Isotopes with high atomic mass can undergo nuclear fission to obtain an increase in binding energy per nucleon. 

From the binding energy curve isotopes with a mass greater than 56 tend to undergo nuclear fission whereas those with a mass less than 56 tend to undergo nuclear fusion in order to increase the binding energy per nucleon.

 

1 eV = 1.602 x 10−19 J. What does 1 MeV equal?

1 MeV = 1.602 x 10−19 x 106 J = 1.602 x 10−13  J = 1.602 x 10−13 x 10−3 kJ = 1.602 x 10−16 kJ.

 

How much binding energy is associated with a mass defect of 0.020 g?

E = mc2 = 2.0 x 10−5 (kg)  (3 x 108 (ms−1))2 = 1.8 x 1012 J = 1.8 x 109 kJ

 

Which gases will effuse 1.5 times faster than sulfur dioxide?

I. ethene

II. nitrogen

III. carbon monoxide

Ethene, nitrogen and carbon monoxide all have the same molecular mass (Mr = 28) (so the answer must be I, II and III). The Mr of SO2 is 64. Relative rate of diffusion of the gases compared to SO2 = √64 ÷ √28 = 8 ÷ 5.29 = 1.5

 

A decay constant has been calculated to be 2.5 x 10−2 years−1. Which is the correct expression for the half-life?

ln 2 = λt½, so t½ = ln 2 ÷ λ. (Since the units of λ are years−1 the correct answer is the only one of the four which gives the answer in years.)

 

An isotope of technetium is used as a tracer in hospitals. It has a half-life of 6.0 hours. If it is prepared at 0800 in the morning how much will be remaining by 1700 on the next day?

100% → 50% → 25% → 12.5% →  6.25% → 3.125% →1.5625%. After 5 half-lives (1400 on the next day) there will be 3.125% remaining and after 6 half-lives (2000 on the next day) there will be 1.5625% remaining.

 

Under the same conditions hydrogen bromide gas effuses 2.25 times slower than another gas. What is the molar molecular mass (in g mol−1) of the other gas?

Rate(X) ÷ rate(HBr) =  2.25 = √M(HBr) ÷ √M(X) =  9 ÷ √M(X) so √M(X) = 9 ÷ 2.25 = 4, so  M(X) = 16.

 

Which methods involving uranium hexafluoride can be used to enrich uranium with 235U.

I. Fractional distillation 

II. Effusion

III. Centrifugation

The difference in the boiling points of 235UF6 and 238UF6 is much too small to be able to separate them by fractional distillation.

 

What is/are the bond angle(s) in a molecule of uranium hexafluoride?

There are six bonding pairs of electrons (electron domains) around the central uranium atom so it is octahedral

 

Ionizing radiation can produce hydroxyl radicals which can damage enzymes and DNA.
Which is the correct Lewis structure for the hydroxyl radical?

The hydroxyl radical is a neutral molecule. It is paramagnetic as it contains an unpaired electron.

 

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