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A student added very dilute sulphuric (VI) acid to four substances and recorded the observations shown in the table below.
For which tests are the observations wrong? Explain
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Give the name of the product formed when magnesium reacts with phosphorus.
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Classify the following processes as either chemical or physical.
ANSWERS
(a) Chemical change
(b) Physical change (c) Chemical change
The figure below represents the set up that was used to crack an alkane.
a) What was the purpose of the sand?
b) After some time, a colourless gas G collected in the test-tube. Describe a chemical test and the observations that would be made in ordered to identify the class of compounds to which gas G belongs.
ANSWERS
(a) Catalyst or words to that effect
(b) Add bromine water or acidified potassium magnate (VII) if they decolorize then gas is either an alkene or an alkynes
Bottles of sodium carbonate, sodium chloride and sugar have lost their labels.
A student prepares and tests an aqueous solution of a sample from each bottle. The results obtained are as shown in the table below. 
Complete the table by filling the correct label for each bottle.
ANSWERS
The structure of methanoic acid is
What is the total number of electrons used for bonding in a molecule of methanoic acid? Give reasons.
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The solubility curve of potassium nitrate is shown below.
a) Determine the solubility of potassium nitrate at 50°C b) Determine the molar concentration of saturated potassium nitrate at 50°C (K=39.0 0= 16.0 N= 14.0 and density of water 1 g/cm3). 
ANSWERS
A student used the set up shown in the diagram below in order to study the reactions of some metals with steam. The experiment was carried out for ten minutes
a) What observation would be made if gas F is ignited?
b) When the experiment was repeated using iron powder instead of magnesium ribbon very little gas F was obtained. i) Give a reason for this observation ii) What change in the conditions of the experiment should the student have made in order to increase the volume of gas F Produced?
ANSWERS
(a) The gas burns with a blue flame
(b) (i) The iron isles reactive than magnesium (ii) Heat the iron powder
a) Draw and name the structure of the compound formed when one mole of ethyne reacts with one mole of hydrogen bromide.
b) Draw the structures of the alkynes whose molecular formula is C4H6
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The standard reduction potentials of two half –cells are:
Ag+(aq) + e → AG(s) ; E = 0.80V 2H2O (l) + 2e → H2 (g) + 2OH (aq); E1 = 0.83V Draw a labelled diagram of an electro chemical cell that can be constructed using the two half –cells
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Starting with 50 cm3 of 2.8M sodium hydroxide, describe how a sample of pure sodium sulphate crystals can be prepared.
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Hydrogen and oxygen can be obtained by electrolysis of acidified water.
Using equations for the reactions at the electrodes, explain why the volume of hydrogen obtained is twice that of oxygen.
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​Related Chemistry Questions and Answers on Electrochemistry Form 4 Level
a) what is meant by molar heat of solution?
b) the lattice energy of sodium bromide and hydration energies of sodium and bromide ions are: 733,406 and 335 kJmol -1 respectively. i) Complete the energy cycle diagram below by inserting the values of ΔH1, ΔH2, and ΔH3 
ii) Determine the molar heat of solution of solid sodium bromide.
ANSWERS
Using dots (.) and crosses (x) , show bonding in:
a) The compound formed when nitrogen reacts with fluorine (Atomic numbers F=9, N=7); b) Sodium oxide.(Atomic numbers Na= 11, 0 = 8)
ANSWERS
When aluminium oxide was electrolysed, 1800kg of aluminium metal were obtained.
a) Write equation for the formation of aluminium metal b) Calculate the quantity of electricity in faradays used (Al=27)
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AuthorMaurice Atika is a teacher and a netprenuer. |
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