These are chemistry questions and answers categorized according to topics, papers i.e. Paper 1 and 2, Levels i.e. form 1 to form 4, kcse year the examination was done and section A or B
Select topic/category to open topical questions from that particular option provided.
a) State three differences between chemical and nuclear reactions. (3mks)
(any three 3mks)
b) Study the figure below and answer the questions that follow
Identify the radiations A, B and C (3mks)
(a) Give the symbols of the o charged particles emitted by a radioactive isotope.
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:
(iv) Nuclear power station
(c) State two dangers associated with radioactivity.
(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
Causes skin cancer;
When tested causes environmental pollution.
Calculate the values of X and Y in the following nuclear equation.
a)Complete the nuclear equation below:
(c)Give one harmful effect of radioisotopes.
The diagram in Figure 6 Shows radiations emitted by a radioactive sample.
A radioactive substance weighing M kg took 1900 years for the original mass to reduce to 15 kg. Given that the half life of the radioactive substance is 380 years;
(a) Determine the original mass of the radioactive substance.
(b) State two uses of radioactivity in medicine. .
(a) distinguish between a neutron and proton
(b) What is meant by a radioactive substance?
(c) State two dangers associated with radioactive substance in the environment
(i) What is the atomic
a. Mass of Y
b. Number of Y
(ii) What name is given to the type of reaction undergone by the isotopes of hydrogen?
(e)(i) What is meant by half-life of a radioactive substance
(ii) 288 g of a radioactive substance decayed to 9 g in 40 days. Determine the half-life of the radioactive substance
Draw a labeled diagram to illustrate how alpha, beta and gamma radiations can be distinguished from each other.
Study the nuclear reaction given below and answer the questions that follow
A radioactive isotope X2 decays by emitting two alpha (a) particles and one beta (β) to from
(a) What is the atomic number of X2?
(b) After 112 days, 1/16 of the mass of X2 remained. Determine the half life of X2
120g of iodine - 131 has a half life of 8 days and decays for 32 days. On the grid provided, plot a graph of the mass of iodine - 131 against time.
The graph below shows the mass of a radioactive isotope plotted against time
(a) Using the graph, determine the half – life of the isotope
(b) Calculate the mass of the isotope present after 32 days
Maurice Atika is a teacher and a netprenuer.