NECO Chemistry Practical Questions and Answers 2022/2023 Examination (Complete Solution)

(2iv)
TEST; To the third portion add AgNO³ solution

OBSERVATION; White Precipitate formed

INFERENCE; SO4²^- , CL^- CO²^- present

(2v)
TEST; To the results obtained in add dilute HNO3 in drops , then excess

OBSERVATION; White Precipitate is insoluble

INFERENCE; CL^- present

(2vi)
TEST; To the results obtained in add NH3 solution

OBSERVATION; White Precipitate dissolves

INFERENCE; CL^- Confirmed

(3ai)
Filtration

(3aii)
Diagram.

(3bi)
I. Methyl Orange
II. Methyl orange
III. Phenolphthalein

(3bii)
A white Precipitate is observed. Effervescence occurs a gas is evolved which change lime water milky.

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NECO Chemistry Specimen 2022

CHEMISTRY PRACTICAL SPECIMEN:

Requirements:
(a) One burette (50cm³)
(b) One pippete (20cm³/25cm³). However, all
candidates in a center must use pipettes of the
same volume.
(c) The usual apparatus and reagents for
qualitative work including:
(i) Dilute sodium hydroxide solution
(ii) Dilute ammonia solution
(iii) Dilute hydrochloric acid
(iv) Barium chloride solution
(v) Distilled water
(vi) Red and Blue litmus paper
(vii) Phenolphtalein
(d) Methyl orange
(e) One boiling tube
(f) Five test tubes
(g) Filtration apparatus
(h) Source of heat
Each candidate should be supplied with the
following: Labelled An, Bn, Cn, where ‘n’ is the
candidate’s serial number.
(a) 150cm³ of chloride acid solution in a bottle
labelled “An”. The acid solution which should
be the same for all candidates will contain
3.4cm³ of the concentrated hydrochloric acid
per dm³ solution.
(b) 150cm³ of sodium hydroxide solution in a
bottle labelled “Bn”. The solution which should
be the same for all candidates will contain
4.0g of sodium hydroxide per dm³ of solution.
(c) One spatulaful of copper (ii)
tetraoxosulphate (vi) salt in a specimen bottle
labelled “Cn”.

The questions below are strictly for practice not the 2021 Chemistry expo.

All your burette readings (initials and final) as well as the size of your pipette must be recorded but no account of experimented procedure is required. All calculations must be done in your booklet.

(b) From your results and the information provided. Calculate the: (i) concentration of C in moldm^-3; (ii) concentration of C in gdm^-3; (iii) molar mass of Na₂CO₃, xH₂O; (iv) the value of x in Na₂CO₃ xH2O. [H = 1.0; C=12.0; O = 16.0; Na =23.0]

Credit will be given for strict adherence to the instruction, for observations precisely recorded and for accurate inferences. All tests, observations and influences must be clearly entered in the booklet in ink at the same time they are made.

2. F is a mixture to two inorganic salts. Carry out the following exercise on F. record your observation and identify any gas(s) evolved. State the conclusions you draw from the result of each test. (a) Put all of F in a beaker and add about 10cm³ of distilled water. Stir well and filter. Keep the filtrate and the residue. (b)(i) To about 2cm³ of the filtrate, add NaOH_(aq) in drops and then in excess (ii) To another 2cm³ portion of the solution, add a few drops of NHO_3(aq)followed by few drops of AgNO_3(aq). (d)(i) Put all the residue into a clean test-tube and add NHO_3(aq) followed by few solution from 2(d)(i) add NaOH_(aq) in drops and then in excess.

3. State what would be observed if the following reactions are carried out in the laboratory: (i) methyl orange is dropped into a solution of lime juice (ii) hydrogen sulphide gas is bubbled through iron (III) chloride solution; (iii) sulphur (IV) oxide gas is bubbled into acidified solution of KMnO4; (iv) ethanoic acid is added to a solution of K₂CO₃.

CHEMISTRY PRACTICALS ANSWERS

Volume of the base used        =          25.00cm³