KCSE CHEMISTRY QUESTIONS AND ANSWERS PER TOPIC
The empirical formula of A is CH2Br. Given that 0.470g of A occupies a volume of 56cm3 at 546K and 1 atmospheric pressure, determine its molecular formula.(H = 1.0, C = 12.0, Br = 80.0, molar gas volume at STP = 22.4 dm3).
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(a) Name two cations that are present in hard water.
(b) Explain how the ion exchange resin softens hard water.
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.
10cm3 of concentrated sulphuric (VI) acid was diluted to 100cm3. 10cm3 of the Resulting solution was neutralised by 36cm3 of 0.1M sodium hydroxide solution. Determine the mass of sulphuric (VI) acid that was in the concentrated acid (S = 32.0; H = 1.0; O = 16.0).
Ammonium ion has the following structure:
Label on the structure:
(a) covalent bond;
(b) coordinate (dative) bond.
Study the information in the table below and answer the questions that follow: A mixture containing 35g of CuS04 and 78g of Pb(N03)2 in l00g of water at 60°C was cooled to 40°C.
(a) Which salt crystallised out? Give a reason
(b) Calculate the mass of the salt that crystallised out.
A sample of water in a beaker was found to boil at 101.5°C at 1 atmospheric pressure.
Assuming that the thermometer was not faulty, explain this observation.
ANSWERS
The table below shows properties of some elements A, B, C and D which belong to the same period of the periodic table. The letters are not the actual symbols of the elements.
(a) Arrange the elements in the order they would appear in the period. Give a reason.
(b) Select the metallic element which is the better conductor of electricity. Give a reason.
ANSWERS
(a) BDACAcross the period the atomic radius decreases.
(b) D Across the period the conductivity increase due to increase in delocalised electrons.
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
Iron (III) oxide was found to be contaminated with copper (II) sulphate. Describe how a pure sample of iron (III) oxide can be obtained.
Charcoal is a fuel that is commonly used for cooking. When it burns it forms two oxides.
(a) Name the two oxides. (b) State one use of any of the two oxides.
ANSWERS
(a) Carbon (IV) Oxide and Carbon (II) Oxide
(b) CO2- Fire extinguishers Fizzy drinks Food preservative . Solvay process . CO -Manufacture of fuel (water gas) Reduction in the extraction of metals Manufacture of methanol |
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