KCSE CHEMISTRY QUESTIONS AND ANSWERS PER TOPIC
Describe how sodium carbonate is used to remove water hardness
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5g of calcium carbonate was strongly heated to a constant mass. Calculate the mass of the solid residue formed (Ca=40 0; C= 12.0; 0= 16.0). (2 marks)
During laboratory preparation of oxygen, manganese(IV) oxide is added to reagent H.
Figure 5 shows an apparatus used to separate a mixture of water and hexene.
A boiling tube filled with chlorine water was inverted in a trough containing the same solution and the set-up left in sunlight for about 2 hours.
Ethene is prepared in the laboratory by dehydration of ethanol.
The graph in Figure 4 was obtained when a certain substance was heated and its temperature recorded at regular intervals.
(a) State the purity of the substance. (I mark)
(b) Explain the answer in (a). (2 marks)
Calculate the mass of Zinc oxide that will just neutralize dilute nitric (V) acid containing 12.6 g of nitric (V) acid in water. (Zn = 65.0; O =16.0, H = 1.0, N = 14.0).
a) State the Boyles Law
b) A gas occupies 500cm3 at 27°C and 100,000 Pa, What will be its volume at O°C and 101325 Pa?
(a) What is meant by lattice energy?
b) Study the energy level diagram below and answer the question that follows
What type of reaction is represented by the diagram?
ANSWERS
(a) Enthalpy change, when one mole of crystal lattice is broken into its ions in gaseous state.
(b) Endothermic reaction (process)
(a) Name the raw material from which sodium is extracted.
(b) Give a reason why sodium is extracted using electrolysis. (c) Give two uses of sodium metal.
ANSWERS
(a)Brine (NaCl)
(b) Sodium is very reactive (use electrolysis) More reactive than carbon. (c) Uses Sodium lamps, coolant in nuclear reactors Sodium cyanide, sodium amalgam Na202 , Extraction of titanium,
(a) Give the name of the first member of the alkene homologous series.
(b) Describe a chemical test that can be used to distinguish butanol from butanoic acid
Sulphur(IV) oxide is prepared in the laboratory using the set-up in Figure 3. Study it and answer the questions that follow.
(a) Identify substance F. (1 mark)
(b) Write an equation for the reaction that takes place in the flask. (1 mark) (c) State the purpose of liquid G. (I mark)
Table 1 shows the properties of two chlorides, D and E.
(a) State the type of bond present in:
A solution contains 40.3 g of substance XOH per litre. 25M cm3 of this solution required 30.0cm3 of 0.3 M sulphuric(Vl) acid for complete neutralisation. (a) Calculate the number of moles of XOH that reacted. (½ mark) (b) Determine the relative atomic mass of X. (1½ marks)
A farmer intended to plant cabbages in his farm. He first tested the pH of the soil and found it to be 3.0. If cabbages do well in alkaline soils, explain the advice that would be given to the farmer in order to realise a high yield. (2 marks)
Hydrogen gas can be prepared by passing steam over heated magnesium ribbon as shown in Figure 2.
(a) Write an equation for the reaction that produces hydrogen gas. (1 mark)
(b) Explain why the delivery tube must be removed from beneath the water before heating is stopped. (1 mark) (c) Explain why sodium metal is not suitable for this experiment. (1 mark)
A monomer has the following structure.
(a) Draw the structure of its polymer that contains three monomers. (1 mark)
(b) A sample of the polymer formed from the monomer has a molecular mass of 4992. Determine the number of monomers that formed the polymer (C= 12; H= 1.0). (2 marks)
A gas jar full of chlorine water was inverted over water and allowed to stand for sometime
a)State and explain two observations made in the gas jar after some time.
b) Write the equation for the reaction between chlorine and hot concentrated potassium hydroxide
a)What is meant by the term radical?
b) The table below contains atoms that form common radicals. Complete the table to show radicals formed from various atoms.
A student used the set up below to prepare a sample of nitrogen gas.
a) State the function of potassium hydroxide in the set up
b) Give a suitable metal M for use in the combustion tube c) Give a reason why the nitrogen gas obtained is not pure.
ANSWERS
(a) It absorbs carbon (IV) oxide present in the air.
(b) Copper /Cu(S) (c) It has rare noble gases which have not been removed / Argon.
a) Name a suitable solvent for extracting an indicator form flowers:
b) Give a reason why the solvent named in (a) above is used
ANSWERS
(a) Acetone / ethanol / propanone / propanol.
(b) The solvent dissolves the organic compound indicator present in the flowers / it is an organic solvent.
Cotton is a natural polymer. State one advantage and one disadvantage of this polymer.
ANSWER
An organic compound had the following composition 37.21% carbon, 7.75% hydrogen and the rest chlorine. Determine the molecular formula of the compound, given that
the molecular mass of the compound is 65. (C=12.0; H=1.0; CL=35.5)
(a) A student electrolyzed dilute sodium chloride solution using inert carbon electrodes. Name the products at:
i)Anode : ii)Cathode: (b) If the experiment was repeated using concentrated sodium chloride instead of dilute sodium chloride solution, write the half equation at the anode. |
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