KCSE CHEMISTRY QUESTIONS AND ANSWERS PER TOPIC
In an experiment, dry hydrogen gas was passed over heated Lead (II) Oxide as shown in the diagram below.
State and explain the observations made in the combustion tube.
ANSWERS
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Iron (III) oxide was found to be contaminated with copper (II) sulphate. Describe how a pure sample of iron (III) oxide can be obtained.
Describe how the PH of anti-acid (Actal) powder can be determined in the laboratory
ANSWERS
State two reasons why hydrogen is not commonly used as a fuel.
ANSWERS
A mixture contains ammonium chloride, copper (II) oxide and sodium chloride.
Describe how each o the substances can be obtained from the mixture.
ANSWERS
Heat the mixture to sublime the ammonium chloride.
Add water to dissolve the sodium chloride ; copper (ii) oxide does not dissolve Filter and evaporate the filtrate to obtain sodium chloride.
Use the information in the table below to answer the questions that follows
Explain the trend in the molar heats of vaporization
Expected Response
Change was greatest with magnesium. Both react with oxygen to form oxides but magnesium reacts with nitrogen to form a nitrite
A water trough, aqueous sodium hydroxide, burning candle, watch class and a graduated gas jar were used in an experimental set up to determine the percentage
of active part of air. Draw a labeled diagram of the set up at the end of the experiment.
Hydrate cobalt(II) chloride exists as pink crystals and anhydrous cobalt(II) chloride is a blue powder. Describe a laboratory experiment that can be used to show that the action of heat on hydrated cobalt(II) chloride is a reversible reaction.
ANSWERS
ANSWERS
(a) Chemical change
(b) Physical change (c) Chemical change
The diagram below shows the physical state of matter. Study it and answer the questions that follow
Identify the processes R, V, w and U
(c) Name one substance which can undergo the process represented by S and T.
Expected Response
A student used the set up shown in the diagram below in order to study the reactions of some metals with steam. The experiment was carried out for ten minutes
a) What observation would be made if gas F is ignited?
b) When the experiment was repeated using iron powder instead of magnesium ribbon very little gas F was obtained. i) Give a reason for this observation ii) What change in the conditions of the experiment should the student have made in order to increase the volume of gas F Produced?
ANSWERS
(a) The gas burns with a blue flame
(b) (i) The iron isles reactive than magnesium (ii) Heat the iron powder
ANSWERS
(a) Water
(b) The second / other product of burning candle is carbon (IV) oxide (l). It can be prevented from getting into the environment by passing it though a hydroxide solution/ alkaline solution e.g. K.O.H NaOH or aqueous ammonia . To form K2CO3
Expected Response
Expected Response
The grid below shows part of a periodic table. The letters do not represent the actual symbols of the elements
Expected Response
ANSWERS
(a)Cooling
(b)Latent heat of fusion
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
When a student was stung by a nettle plant, a teacher applied an aqueous solution of ammonia to the affected area of the skin and the student was relieved of pain .Explain.
ANSWERS
ANSWERS
C- unburnt gas
D- Luminous yellow flame
ANSWERS
a)They gain energy and move faster. The intermolecular distance increases.
b)XY c)The energy supplied changes molecules of water from liquid to Gaseous state.
ANSWERS
a)V1 and V3
b)Add petrol to the mixture. Filter. V2 is the residue. Filtrate is V4 Distill the filtrate.
ANSWERS
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