# WAEC 2019 Chemistry (Practical) Expo Questions And Answers Expo Runs

WAEC 2019 Chemistry Practical Expo, West Africa Examination Council WAEC 2019 Chemistry (Practical) Expo Questions And Answers Expo Runs Now Posted for free. This is to Inform the WAEC 2019 Candidates, that the Eduwapaz™ is ready to Provide the Solutions for the WAEC 2019 Chemistry Practical Expo Answers (May/June).

Here Is The Verified Waec 2019/2020 Chemistry Practical Expo Questions And Answers – May/June Expo Runz Eduwapaz.com

## ALWAYS SUBSCRIBE IF YOU DONT WANT DELAY OR LATE ANSWERS.. WE FOCUS MORE ON SUBSCRIBERS BECAUSE THEY ARE THE VERY SERIOUS One. (1a)
DRAW A TABLE WITH THE FOLLOWING

Final |13.60|15.50|14.80|12.50
Initial |1.00 |3.10 |2.40 |0.00
Vol. acid used |12.60|12.60|12.40|12.50

Volume of S2O3²- =12.60+12.40+12.50/3
=37.50/3
=12.50cm³

(1bi)
Conc. in g/dm³ = molar mass * conc in mol/dm³
But molar mass of Na2S2O3
=(23*2)+(32*2)+(16*3)
=46 + 64 + 48
=158g/mol
Therefore 15.8g/dm³ = 158g/mol * conc of A in mol/dm³

Conc of A in mol/dm³ = 15.8/158
=0.1mol/dm³

(1bii)
Using CaVa/CbVb = na/nb
0.1*12.50/Cb * 25.00 = 2/1

50Cb = 1.25
Cb = 1.25/50
Cb = 0.025mol/dm³

The conc of I2 in B = 0.025mol/dm³

(1biii)
Gram conc of I2 = molar mass * molar conc
= (127*2)*0.025
=6.35g/dm³

Percentage mass of I2 in sample = 6.35/9.0 *100%
= 0.7056 * 100%
=70.56%

(1c)
There have to be a change in the colour of the mixture before it is added. The end point is known when the blue colour formed as starch is added, changes to colourless

====================

(2a)
Test: C + Water and filtered
Observation: part of C dissolves, colour less filtrate is formed
Inference: C is a mixture of a soluble salt

(2bi)
Test: 2cm^2 of filterate of salt C + AgNO3(aq) then dilute HNO3
Observation: white precipitate is formed
Inference: Cl^- present

(2bii)
Test: Solution im 2(b)(i) + excess NH3 solution
Observation: precipitate disorder in excess solution of NH3
Inference; Cl^- confirmed

(2ci)
Test: Resident + dilute HCl + shake
Observation; residue dissolved to form a blue solution
Inference; Cu^2+ present

(2cii)
Test; solution in 2(c)(i) + NH3 solution in drops and then in excess.
Observation: light pale blue precipitate is formed precipitate dissolved in excess solution of NH3 to give a deep blue solution
Inference; Cu^2+ confirmed.

=====================

(3ai)
On adding BaCl2 solutions to a portion of saturated Na2CO3 precipitate is formed,precipitate dissolves on adding excess dilute HCl

(3aii)
Q is reducing agent like SO2, H2S, CO

(3bi)
calcium oxide(Cao)

(3bii)
concentrated H2SO4

(3c)
NaOH pellet is delinquescent because it absorb moisture from the atmosphere to form solution

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