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◉ NECO 2019 ASSISTANCE ◉ 2019 WAEC ASSISTANCE

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Get A1, B2, B3 In NABTEB 2019 Examination.

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## How to Get 2019 NECO 2019 JUNE/JULY CHEMISTRY PRACTICAL Question Paper.

(1)
The volume or pipette used 25.00cm³

In a tabular form
Titrations |rough |1st|2nd|3rd|
Vol of A used |21.00|20.30|20.40|20.50

(1ai)
Average volume of A = 20.30+20.40+20.50/3
=61.2/3
=20.40cm³

(1aii)
H2X(aq) + 2NaOH(aq)–>Na2X(aq) + 2H2O(l)

(1bi)
Mass conc. of B = 1g/250cm³
= 1g/0.25dm³ = 4g/dm³
Using :
Molar conc. = mass conc./molar mass
= 4/(23+16+1) = 4/40 = 0.1mol/dm³

(1bii)
Using CAVA/CBVB = nA/nB
CA = CBVBnA/VAnB
CA = 0.1×25×1/20.4×2
Concentration of A = 0.06127mol/dm³

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