K.C.S.E Chemistry Q & A-MODEL 2017.PP2.Q N.7

23/11/2020

KCSE Chemistry 2017 Topical Questions and Answers

All Questions Featuring Chemistry Form 1, Form 2, Form 3, Form 4, Paper 1, Paper 2 and Paper 3

The decay rates of a sample of a radioisotope of bismuth at different time intervals is indicated in the following table.

(a)(i) Draw a graph of disintegration rate against time.
(ii) Determine the half-life of bismuth.
(iii) What would be the effect on the curve if half the amount of sample of bismuth were used.
(b) Radioactivity has several applications. State one application of radioactivity in:
(i) Medicine
(ii) Agriculture
(iii) Tracers
(iv) Nuclear power station
(c) State two dangers associated with radioactivity.

ANSWERS

(ii) It would have no effect on the curve as the quantity of bismuth does not affect half-life.
(b)(i)Applications in medicine
Sterilizing surgical instruments.
Destroying cancerous tissues during radiotherapy.
Provide power to the heart pace setters.
(ii) Applications in agriculture
Monitor photosynthesis and other related processes.
Preservation of foodstuffs, by exposing
Micro-organisms to gamma rays.
Rate of absorption of a fertilizer by the plant.
(iii)Applications in Tracers
Detecting leakages in underground water or oil pipes.
(iv)Applications in Nuclear power stations.
To generate electricity.
(d) Dangers of radioactivity
Long term exposure causes genetic mutation;
Radioisotopes can be used as weapon of mass
Destruction;
Causes skin cancer;
When tested causes environmental pollution.