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WAEC 2020 Chemistry Practical Question And Answer


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How to Get 2020 WAEC  CHEMISTRY PRACTICAL Question Paper.

Follow the steps below to get your waec CHEMISTRY questions and answers 1 hours before your exam time.

2020 WAEC-CHEMISTRY-PRACTICAL ANSWERS
=================================
(1a)
In a tabular form

Burette Reading|1st reading|2nd reading|3rd reading
Final |15.25|0.00|45.79|
Initial|0.00||15.25|30.53|
Volume of acid used |15.25|15.28|15.26

Average volume of acid used = 15.25 + 15.26/2
= 15.255cm³
=15.26cm³

(1bi)
Given: Mass of conc of A = 5g/500cm³ = 5g/0.5dm³
Ca = 10g/dm³

A is HNO3
Therefore; Molar mass = 1+14+(16×3)
= 15+48
=63g/mol

Molarity of A = gram conc/molar mass
Ca = 10/63 = 0.1587mol/dm³

(1bii)
Using CaVa/CbVb = nA/nB
With reacting equation:
HNO3 +NaOH–>NaNO3 + H2O
nA = 1, nB = 1
0.1587×15.26/Cb×25.00 = 1/1
25Cb = 0.1587×15.26
CB = 0.1587×15.26/25
CB = 0.09687mol/dm³

(1biii)
B is NaOH
Molar mass = 23+16+1
=40g/mol
Conc of B in g/dm³ = molarity×molar mass
=0.09687×40
=3.8748g/dm³

(1biv)
No of moles present in 250cm³ of NaOH is
= molar conc. × volume
= 0.09687 × 250/1000
= 0.0242 moles

Mole ratio of NaOH and NaNO3 is 1:1
No of moles of NaNO3 which reacted is 0.0242
Mass of NaNO3 formed = molar mass × no of moles
= 85 × 0.0242
=2.057grams
=================================
(2a)
TEST
C + burning splint

OBSERVATION
Sample C bursts into flame
It burns with non-smoking blue flame, without soot.
Colourless gas that turns wet with blue litmus paper faint red and turns lime water milky is present

INFERENCE
C is volatile and flammable. The gas is CO2 from combustion of a saturated organic compound.

(2bi)
TEST
C + distilled water + Shake

OBSERVATION
Clear or colourless solution is observed

INFERENCE
C is miscible with water

(2bii)
TEST
C + Acidified K2Cr2O7

OBSERVATION
Orange color of K2Cr2O7 Solution turns pale green and eventually pale blue on cooling

INFERENCE
C is a reducing agent

(2c)
TEST
D + C + 10% NaOH + Shake

OBSERVATION
D dissolve slowly in C and produces reddish brown solution

Reddish brown solution turns yellow precipitate. The precipitate has an antiseptic odour

INFERENCE
D is soluble in organic solvents

Ethanol, ethanal or a secondary alkanol is present

(2d)
Compound belongs to the class of secondary alkanol
=================================
(3ai)
Zinc nitrate

(3aii)
2 Zn(NO 3 )2 —–>2 ZnO + 4 NO 2 + O 2

(3aiii)
It turns white when cold from it yellow colour when it was hot

(3b)
Pipette / measure 50.0cm3 of the stock solution into a 250
cm3 volumetric flask (containing some distilled water). Shake / swirl and add more distilled water until the mark is reached.

(3c)
Al2(SO4)3 – turns blue litmus red
=================================
Completed!!!!!!!


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3 Comments

  1. I like this grouo

    by Prince mathew on Aug 31, 2020 at Reply

  2. chemistry practical question and answer

    by onu agwu olughu on Aug 18, 2020 at Reply

  3. waec answers

    by adams magaji on Aug 17, 2020 at Reply

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