2018/2019 Nabteb Chemistry Practical answer solution


From the relation n = cv/100 = m/M
0.100×250/1000 = m/106
.:. m =2.65g
(i) Hence, put all of 2.65g of Na2CO3 in a beaker(250cm) and add water.
(ii) Stir well until all the solids dissolves.
(iii) Then, transfer it to volumetric capacity 1dm3.
(iv) Allow it to stand, then transfer to 250cm³ capacity volumetric flask.

(i) 1000cm³ volumetric flask
(ii) Conical flask

(i) The burette should be washed with water and properly rinsed with acid
(ii) The Na2CO3 should be sucked carefully to avoid interference with air
(iii) The titration should stop immediately a color change is noticed in the conical flask

2HCl(aq) + Na2CO3(aq) -> 2NaCl(aq) + H2O(l) + CO2(g)

(i) VA = 29.90cm³, VB = 25.0cm³
CB = 0.100 mol/dm3
Using the relation CAVA/CBVB = nA/nB
Where nA = 2, nB = 1
.:. CAx29.90/0.100×25.0 = 2/1
.:. CA = 0.100x2x25/29.90
CA = 0.167 moldm-³
.:. Concentration of HCl in moldm-³ is 0.167moldm-³

(ii) Finding the Concentration of HCl in gdm-³;
Recall that mass concentration of HCl = molar conc x molar mass
Where molar conc of HCl = 0.167 x 36.5
Molar mass of HCl = 1+35.5 = 36.5g/mol
.:. Mass conc = 0.167 x 36.5
= 6.10gdm-³


Gas: Hydrogen Sulphide
Anion: S²-

Gas: Carbon (iv) Oxide
Anion: CO₃²-

Gas: Hydrogen Chloride
Anion: Cl-

Gas: Sulphur (iv) Oxide
Anion: SO₃²-

Add dil HCl to both; Pb²+ is insoluble while Al³+ is soluble


32 Seconds

80 seconds

Rate of reaction = volume of hydrogen evolved(cm³)/Time taken(s)
= 14cm³/30cm³
= 0.467cm³/sec



Clay triangle

Kipp’s apparatus

Ball mill

Delivery tube

(i) A gas with pop sound is evolved.
(ii) A white solid salt is formed

(i) Produces an irritating smell gas which forms white dense fumes with ammonia. The gas is HCl
(ii) It is also produces cholroethane

(i) Ethane is produced
(ii) Ethoxyethane is also produced

(i) Produces a pungent vapour ethanol
(ii) Ethanonic acid is also produced


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