More Lessons for IGCSE Chemistry
A series of free IGCSE Chemistry Activities and Experiments (Cambridge IGCSE Chemistry).
Look up the following tests for cations, anions, gases, hydrocarbons etc. if necessary:
Collect and Identify Gases
Identify Hydrocarbons and Others
Solid E was analysed. E was an aluminium salt. Some of the observations are shown below.
Appearance of solid E - white crystalline solid.
A little of solid E was heated in a test-tube - colourless drops of liquid formed at the top of the tube.
(a) A little of solid E was dissolved in distilled water.
The solution was divided into four test-tubes and the following tests were carried out.
Complete the observations for tests 2 and 3.
(i) Test 2:
Drops of aqueous sodium hydroxide were added to the first test-tube.
(ii) Excess sodium hydroxide was then added.
(iii) Test 3:
Drops of aqueous ammonia solution were added to the second test-tube. Excess ammonia solution was then added.
observations ______________ 
Two further tests are carried out and the following observations made.
tests on solution of E observations
To the third test-tube of solution, dilute hydrochloric acid was added, followed by barium nitrate solution - no reaction
To the fourth test-tube of solution, aqueous sodium hydroxide and aluminium foil were added.
The mixture was warmed carefully - effervescence, pungent gas given off, gas turned damp litmus paper blue
(b) What does test 1 tell you about solid E? __________
(c) Identify the gas given off in test 5. __________ 
(d) What conclusions can you draw about solid E? __________ 
(e) Test 5 states that the mixture should be warmed carefully.
In terms of safety, explain why it is necessary to warm carefully _________ 
(a) (i) white precipitate 
(ii) precipitate dissolves in excess; 
(iii) white precipitate; 
no change / precipitate remains; 
(b) contains water / hydrated 
(c) ammonia, not: ammonium 
(d) Any two from:
hydrated salt / contains water;
it is not a sulfate; 
(e) sodium hydroxide is hazardous / irritant / caustic; 
boiling causes mixture to spit / blow-out; 
E-numbers identify chemicals which are added to foods.
(a) E210 is benzoic acid. How could you show that a solution of benzoic acid is a weak acid?
result __________ 
(b) E110 is Sunset Yellow.
Outline a method you could use to show the presence of E110 in a food colouring.
You may draw a diagram to help answer the question. 
(a) Universal indicator / pH paper; 
pH of 4–6 / yellow / orange; 
note: any suitable test with appropriate result
(b) Any four from:
description of applying food colouring to paper;
use of solvent;
results / number of spots;
compare results to known sample / reference to Rf value; 
marks can be obtained from a labelled diagram
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