If you are a candidate who is preparing for this year’s chemistry practical examination, here is a good new for you. The post you are reading at this moment will show all the possible test, observation and inferences which you should expect in the coming exam.
So, get your pen and paper as we dive in together! The sample you are going to see in your exam is mixture of organic and inorganic compounds ( starch and Copper (II) tetraoxosulphate (VI) salt). Let us take in head on with this model exam question below:
F is a mixture of organic and inorganic compounds.
a. Put F into a test-tube and add about 10cm3 of distilled water, filter, keep the residue and divide into five portions.
II. To the first portion, add Zinc dust.
III. To the second portion, add dilute NaOH solution in drops then in excess.
IV. To the third portion, add aqueous ammonia in drops then excess.
b. To the four portion, add Pb(NO3)2 solution then dilute HNO3 solution.
II. To the last portion, add BaCl2 solution and dilute HCl
III. To the residue, add few drops of iodine solution
S/n | Test | Observation | Inference |
a(I) | F plus distilled water, filter,keep the residue and divide the filtrate into five portions | Partially soluble,white residue and blue filtrate | A mixture of soluble and insoluble compounds, transition ions likely present |
(II) | To the first portion, add zinc dust | Blue colour disappears, brown precioitate formed | Zinc displaced the metallic ions in the solution |
(III) | To the next portion, add dilute NaOH solution in drops then in excess | Pale bles gelatineous precipitate insoluble in excess | Cu2+ likely present |
(IV) | To another portion, add aqueous ammonia in drops then excess | Pale blue gelatinous precipitate soluble in excess and gives a deep blue solution | Cu2+ confirmed |
b(I) | To the four portion, add Pb(NO3)2 solution then dilute HNO3 acid | White precipitate formed Insoluble in acid | CO32-, SO32-, SO42- likely present SO42- present |
(II) | To the last portion, add BaCl2 then Dilute HCl | White precipitate formed Insoluble in the acid | CO32-, SO32-, SO42- likely present SO42- confirmed |
(III) | To the residue, add few drops of iodine solution | Blue-black colour obtained | Starch confirmed |
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