KCSE CHEMISTRY QUESTIONS AND ANSWERS PER TOPIC
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
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The diagram below represents the set-up that was used to prepare and collect hydrogen chloride gas in the laboratory.
State the purpose of concentrated sulphuric (VI) acid in the wash bottle.
Write an equation for the reaction between dry hydrogen chloride gas and heated iron.
ANSWERS
It is a drying agent.
Fe(s) + 2HCI(g) → FeCI2(s) +H2(g)
Aluminium is both malleable and ductile.
(a)What is meant by? (i) Malleable: (ii)Ductile (b)State One use of aluminium based on: (i)malleability (ii)ductility
ANSWERS
(a) (i) Can be hammered into sheets.
(ii)Can be drawn into wires. (b)(i) Making of sufurias/ motor vehicle parts/ aeroplane parts,window / door flames, cups, plates, packaging materials, pans, making sheets/ roof. (ii)electricity cables/ wires.
When 8.53g of sodium nitrate were heated in an open test-tube, the mass of oxygen gas produced was 0.83 g . Given the equation of the reaction as;
2NaNO 3 (s) -> 2NaNO 2 (s) + O 2 (g) Calculate the percentage of sodium nitrate that was converted to sodium nitrite. (Na = 23.0, N = 14.0, O = 16.0)
Ammonium ion has the following structure
Label on the structure:
(a) covalent bond; (b) coordinate (dative) bond.
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
The set up below was used to investigate the reaction between dry hydrogen gas and copper
(a) Name substance A.
(b) State the observation made in the combustion tube. (c) Explain the observation stated in (b) above.
ANSWERS
(a) Fused anhydrous calcium chloride
Cao: fused CaCl2 (b) Black CuO changes to brown Cu metal Formation of colourless liquid on the cooler parts of the combustion tube. (c) Copper (II) oxide is reduced by hydrogen to copper metal while hydrogen is oxidized to water /CuO reduced to Cu /H2 Oxidized to H2O
The figure below shows an energy cycle.
(a)Give the name of the enthalpy change ΔH1.
(b)Determine the value of ΔH3.
An alknal has the following composition by mass: hydrogen 13.5%, oxygen 21.6% and carbon 64.9%
(a)Determine the empirical formula of the alcohol(C=12.0; H=1.0’ 0=16.0). (b)Given that empirical formula and the molecular formula of the alkanol are the same,draw the structure of the alkonol
A student investigated the effect of an electric current by passing it through some substances. The student used inert electrodes, and connected a bulb to the circuit. The table below shows the substances used and their
states.
(a) In which experiment did the bulb not light?
(b) Explain your answer in (a) above.
ANSWERS
(a) 1 and 3
(b)In 1 ions K2CO3 are held rigidly within the crystal cannot move (no mobile ions) In 3 sugar exist as molecule hence no mobile ions. |
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