An underground water pipe has cracked and water is leaking into the surrounding ground.
Fig. 1.1 shows a technician locating the position of the leak.

Fig: 1.1
A radioactive isotope is introduced into the water supply and the water that leaks from
the crack is radioactive.
The technician tries to locate an area above the pipe where the radioactive count rate is
higher than in the surrounding area.

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MARKS
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(a) State the type of radiation that must be emitted by the isotope for the leak to be
detected.
[1]
(b) The half-life of the isotope used is 6.0 hours.
Explain why an isotope with this half-life is suitable.

[1]
2. A certain element is known to exist as two different isotopes.
(a) State one thing that is the same for atoms of both isotopes.
[1]
(b) State one thing that is different between atoms of these two isotopes.
[1]
(c) An atom of one of these isotopes is unstable and decays into a different element by
emitting a β-particle.
(i) State one thing about the atom that remains the same during this decay.
[1]
(ii) State one thing about the atom that changes as a result of this decay.
[1]
3. The equation for the reaction that produces ammonium nitrate is:
NH3 + HNO3 → NH4NO3
Calculate the number of tonnes of ammonium nitrate that can be made from 68
tonnes of ammonia?
…………………………………………………………………………………………… ……………………………………………………………
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…………………………………………………………………………………………… ……………………………………………………… [2]
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