KCSE CHEMISTRY QUESTIONS AND ANSWERS PER TOPIC
ANSWERS
(a)Amphoteric
(b)Lead (II), Zinc and Aluminium
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Starting with copper metal, describe how a sample of crystals of copper (II) chloride may be prepared in the laboratory.
ANSWER
Samples of urine from three participants F, G and H at an international sports meeting were spotted onto a chromatography paper alongside two from illegal drugs A1 and A2.
A chromatogram was run using methanol. The figure below shows the chromatogram.
a) Identify the athlete who had used an illegal drug.
b) Which drug is more soluble in methanol?
ANSWERS
(a)A1
(b)A1 using baseline
ANSWER
In an experiment, a test-tube full of chlorine water was inverted in chlorine water as shown in the diagram below and the set up left in sunlight for one day.
After one day, a gas was found to have collected in the test-tube
a) Identify the gas. b) What will happen to the PH of the solution in the beaker after one day? Give an explanation.
A sample of water drawn from a river passing through an agricultural district was divided into two portions. The first portion gave a white precipitate when acidified barium chloride was added. The second portion when warmed with aqueous sodium hydroxide gave a colourless gas, which turned a moist red litmus paper blue.
On complete combustion of a sample of hydrocarbon, 3.52 gm of carbon dioxide and 1.44 gm of water were formed. Determine the molecular formula of the hydrocarbon.
(Relative molecular masses of hydrocarbon = 56, carbon dioxide 44, water = 18 and relative atomic masses H = 1.0 and c = 12.0)
Give one advantage and one disadvantage of using petrol containing tetraethyl lead in motor vehicles.
Expected Response
Advantage
Expected response
Add water to the solid mixture A dissolves while B does Not
The table below gives atomic numbers of elements represented b the letters A, B, C and D.
Use the information to answer the questions that follow.
a) Name the type of bonding that exists in the compound formed when A and D react b) Select the letter which represents the best oxidizing agent. Give a reason for your answer.
ANSWERS
(a)Ionic/ electrovalent
(b)Has 7 electrons in its outermost energy level and hence easily gains an electron to complete the octet or it is most electronegative.
When magnesium was burnt in air, a solid mixture was formed. On addition of water to the mixture a gas which turned moist red litmus paper blue was evolved. Explain these observations.
Zinc reacts with both concentrated and dilute sulphuric (VI) acid. Write equations for two reactions.
a) State the observation made at the end of the experiment when a mixture of iron powder and sulphur is heated in a test tube.
b) Write an equation for the reaction the product in (a) above and dilute hydrochloric acid. c) When a mixture of iron powder and sulphur is heated, it glows more brightly than that of iron fillings and sulphur. Explain this observation
ANSWERS
An isotope of Uranium 234U, decays by emission of an alpha particle to thorium 92
ANSWERS
Phosphoric acid is manufactured from calcium phosphate according to the following equation.
Ca3(PO4)2(s) + 3H2SO4(l) → 2H3PO4(aq) + 3 CaSO4(s) Calculate the mass in (Kg) of phosphoric acid that would be obtained if 155 Kg of calcium phosphate reacted completely with the acid (Ca=40, P=31, S=32, O=16, H=1)
The structure of a detergent is
a) Write the molecular formula of the detergent.
b) What type of detergent is represented by the formula? c) When this type of detergent is used to wash linen in hard water, spots (marks) are left on the linen. Write the formula of the substance responsible for the spots
When a hydrated sample of calcium sulphate CaSO4 .XH2O was heated until all the water was lost, the following data recorded;
Mass of crucible = 30.296 g Mass of crucible +hydrated salt = 33.111 g Mass of crucible + anhydrous salt = 32.781 g Determine the empirical formula of the hydrated salt (Relative formula mass of CaSO4 =136, H2O =18).
(a) The diagram below represents a set up that was used to obtain dry nitrogen from air. Study it and answer the questions that follow
Related Chemistry Questions and Answers on ​nitrogen and its compounds form 3 level |
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