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
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a) The solubility of the salt (2mks)b) The percentage of the salt in the saturated solution (1mk)
You are provided with solid potassium hydrogen carbonate. Describe how a solid sample of potassium nitrate can be prepared.
ANSWERS
Measure a certain volume of dilute nitric(V) acid and place it in a beaker;
Add potassium hydrogen carbonate little by little as the mixture is stirred until effervescence stops; Evaporate the solution to saturation and allow to cool for crystals to form; Dry the crystals in between filter papers.
Describe an experiment to show that group one elements react with cold water to form alkaline Solutions
ANSWERS
(a) Define a soluble base.
(b) Aqueous solutions of 2M ethanoic acid and 2M nitric(V) acid were tested for electrical conductivity. Which solution is a better conductor of electricity? Explain.
ANSWERS
(a)A soluble base is a substance that dissociates in water to produce hydroxide ions as the only negative ions.
(b)Nitric(V) acid. This is because nitric(V) acid is a strong acid and dissociates completely in solution producing many H+ ions.
Starting with copper, describe how a pure sample of copper(II) carbonate can be prepared.
A sample of water is suspected to contain sulphate ions. Describe an experiment that can be carried out to determine the presence of sulphate ions.
A mixture contains ammonium chloride, copper (II) oxide and sodium chloride. Describe how each of the substances can be obtained form the mixture.
ANSWERS
A compound whose general formula is M(OH)3 reacts as shown by the equation below.
(a) What name is given to compounds which behave like M(OH) 3 in the two reactions.
(b) Name two elements whose hydroxides behave like that of M.
ANSWERS
(a) Amphoteric
(b)Lead, Zinc and Aluminium
Iron (III) oxide was found to be contaminated with copper (II) sulphate. Describe how a pure sample of iron (III) oxide can be obtained.
ANSWERS
Starting with sodium metal, describe how a sample of crystals of sodium hydrogen carbonate may be prepared.
ANSWERS
React sodium with water to get sodium hydroxide. Bubble into this solution excess carbon (IV) oxide to get sodium hydrogen carbonate
Starting with copper turnings. describe how a sample of copper(II) sulphate crystals can be prepared in the laboratory. (3 marks)
Starting with barium nitrate solution, describe how a pure sample of barium carbonate can be prepared in the laboratory.
ANSWERS
Describe how samples of lead (II) sulphate, ammonium chloride and sodium chloride can be obtained from a mixture of the three.
ANSWERS
(a) The scheme below shows some of the reaction of solution D. Study it and answer the questions that follow
(i) Give a possible caution present in solution D
(ii) Write an ionic equation for the reaction in Step II (iii) What observations would be made in Step V? Give a reason (iv) Explain why the total volume of hydrogen gas produced in step 1 was found to be very low although calcium and solution D were in excess. (v) State one use of substance E. (b)Starting with solid sodium chloride, describe how a pure sample of lead (II) Chloride can be prepared in the laboratory (c) (i) State a property of anhydrous calcium chloride which makes it suitable for use as a drying agent for chlorine gas. (ii) Name another substance that can be used to dry chlorine gas
Starting with zinc sulphate solution, describe how a sample of zinc oxide can be obtained
When dilute hydrochloric acid was reacted with solid B, a colourless gas which extinguished a burning splint was produced. When an aqueous solution of solid B was tested with a blue litmus paper, the paper turned red / pink.
(a) Identify the anion present in solid B. (b) Write an ionic equation for the reaction between solid B and dilute hydrochloric acid.
By using aqueous sodium chloride, describe how a student can distinguish calcium ions from lead ions.
The diagram below illustrates a method of preparing salts by direct synthesis
(a) This method can be used to prepare either aluminum chloride or iron (III) chloride.
Explain why it cannot be used to prepare sodium chloride. (b) Describe how a sample of sodium chloride can be prepared in the laboratory by direct synthesis.
ANSWERS
(a) It does not sublime.
(b) Cut a piece of Sodium metal, place it on a deflagrating spoon. heat it briefly then lower it into a gas jar of chlorine. It will continue burning forming Sodium Chloride.
Write equations to show the effect of heat on each of the following:
(a) Sodium hydrogen carbonate (b) Silver nitrate (c) Anhydrous iron (II) sulphate
How would you obtain a sample of pure iodine from a mixture of iodine and lead sulphate?
Expected Response
Heat the mixture iodine sublimes and can be collected from the cool part of the test tube.
(a) A student was supplied with a colourless liquid suspected to be water
The flow chart below shows the various stages of water treatment. Study it and answer the questions that follow
II Addition of sodium hypochlorite (c) It was confirmed that magnesium sulphate was present in the tap water
Distinguish between the terms deliquescent and efflorescent as used in chemistry
ANSWERS
Describe how a solid sample of the double salt, ammonium iron(II) sulphate, can be prepared using the following reagents; Aqueous ammonia, sulphuric(VI) acid and iron metal.
ANSWERS
a) Distinguish between a deliquescent and a hygroscopic substance.
b) Give one use of hygroscopic substance in the laboratory.
ANSWERS
(a)Deliquescent - a substance that absorbs water from the atmosphere and changes into a solution.
Hygroscopic — a substance that absorbs water from the atmosphere but just becomes wet. (b)drying agent. |
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