KCSE CHEMISTRY QUESTIONS AND ANSWERS PER TOPIC
A given volume of ozone, (O3) diffused from a certain apparatus in 96 seconds. Calculate the time taken by an equal volume of carbon dioxide (CO2) to diffuse under the same conditions (O = 16.0, C = 12.0)
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Study the set- up below and answer the questions that follow
(a) Write an equation for the reaction, which take place in the combustion tube
(b) What property of gas Z allows it to be collected as shown in the diagram
Compound Q is a solid with a giant ionic structure. In what form would the compound conduct an electric current
Expected Response
16. When dissolves in water or fused / molten state
State any two differences between luminous and non – luminous flames
The table below shows the tests carried out on separate samples of water drawn from a well and the results obtained
(a) Identify the cation and the anion present in the water
Cation Anion (b) Write an ionic equation for the reaction which takes place in test (iii) A radioactive isotope X2 decays by emitting two alpha (a) particles and one beta (β) to from 214 Bi 83 (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
Expected Response
20.0cm3 of a solution containing 4 gm per litre of sodium hydroxide was neutralized by 8.0cm3 of dilute sulphuric acid. Calculate the concentration of sulphuric acid in moles per litre (Na = 23.0, O = 16.0, H = 1.0)
A student set up the apparatus shown below to prepare ammonia gas and react it with copper (II) sulphate solution
(a) Identify solution V
(b) State the observations which were made in the beaker
Expected Response
Use the scheme below to answer the questions that follow
(a) Identify the solid
H J (b) State one commercial use of solid J
A hydrocarbon P was found to decolourise bromine water. On complete combustion of 2 moles of P, 6 moles of carbon dioxide and 6 moles of water were formed
Study the solubility curves below and answer the questions that follows
What happens when a solution containing 40gm of potassium chlorate and 40gm of potassium nitrate in 100gm of water at 900C is cooled to 400C? Explain
Give two reasons why helium is used in weather balloons
Expected Response
Starting with copper metal, describe how a solid samples of copper (II) carbonate can be prepared.
The equation below represents a redox reaction
a) Write down the equation for the reduction process
b) Which substance is oxidized
The information below relates to elements S,T,U and X. ( the letters do not represents the actual symbols of the elements.
Both T and X are in group II of the periodic Table) (b) Arrange the elements in order of their increasing reactivity
When a current of 1.5 amperes was passed though a cell containing m3+ ions of a metal M for 15 minutes, the mass of the cathode increased by 0.26g.
(1 Faraday = 96500 coulombs) (a) Calculate the quantity of electricity used (b) Determine the relative atomic mass of metal M
The simplified flow chart shows some of the steps in the manufacture of sodium carbonate by the Solvay process
(a) Identify substance L
(b) Name the process – taking place in step II (c) Write an equation for the reaction, which takes place in step III
Explain the change in mass that occurs when the following substances are separately heated in open crucibles
(a) Copper metal (b) Copper (II) nitrate
Expected Response
a) Mass increases because oxygen combine with copper metal
b) Mass decreases it decomposes into gases that escape.
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).
(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.
Study the information in the table below and answer the questions that follow. The letters do not represent the symbols of the elements.
a) Write the electrons arrangement for the atom formed by elements and M and Q
b) Select an element which is
d) Element R lodes its outermost electron more readily than I. Explain e) Using dots(.) and crosses (x) to represent outermost electrons show bonding in the compound formed elements N and Q. f) Explain why the melting point elements M is higher than that of element . g) Describe how a solid mixture of sulphate of R and lead sulphate can be separated into solid samples.
a) The flow chart below shows a sequence of reactions starting with.
Study and answer the questions that follow.
Cu = 63.5, Fe = 56.0
a) The diagram below shows a set –up used by as a student in an attempt to prepare and collect oxygen gas
c) The reaction between sulphur dioxide and oxygen to form trioxide in the contact process in exothermic. Factory manufacturing sulphuric acid by contact process produces 350kg of sulphur trioxide per day (conditions) for the reaction catalyst. 2 atmospheres pressure and temperatures between. (400 – 5000C) i) What is meant by an exothermic reaction? ii) How would the yield per day of sulphur trioxide be affected Temperatures lower than 40000C are used? Explain.
a) When an organic compound Y is reacted with aqueous sodium carbonate, it produces carbon dioxide reacts with propanol to form a sweet smelling compound Z whose formula is.
c) The scheme below was used to prepare a cleaning agent. Study and answer the questions that follow.
i) What name is given to the type of cleaning agent prepared by the method shown in the scheme?
ii) Name one chemical substance added in step II iii) What is the purpose of adding the elements substance names in C(ii) above. iv) Explain how an aqueous solution of the cleansing removes oil from utensils during washing. |
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