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# NECO 2017 Chemistry Practical Expo Answer – June/July

NECO Chemistry Practical Questions and Answer Solution – May/June 2017 Expo Runz

2017 NECO CHEMISTRY PRACTICAL SOLUTION
NO1)
Note:
Candidates are strongly advised to check which size of pipette was used by their school.
We used 25cm³
—————————
If your school used 20cm³, all you need do is use it in place of 25cm³ anywhere we used it and calculate accordingly
NOTE:ALL MAKE USE OF YOUR SCHOOL ENDS POINT
Volume of Pipette used 25.0cm^3
Titration | Rough | First | Second | Third&nbsp;
Final burette reading (cm^3) | 22.50 | 45.10 | 32.65 | 27.60
Intial burette reading (cm^3) | 0.00 | 22.50 | 10.00 | 5.00
Volume of A used (cm^3) | 22.50 | 22.60 | 22.65 | 22.70
1a) Average volume of A = 22.60 + 22.65 + 22.70/3
= 22.65cm^3
1bi) GIVEN: CB = 0.10moldm^-3
VB = 25cm^3
CA = ?
VA = 22.65cm^3
Equation of reaction:
H2C2O4(aq) + 2NaOH(aq) ====> Na2C2O4(aq) + 2H2O(l)
hence, nA = 1
Nb = 2
Using CAVA /CBVB = nA/nB
CA = CBVBnA/VanB
=0.10 × 25 × 1/22.65 × 2
CA = 0.055 moldm^-3
Concentration of A in moldm^-3 = 0.055
bii) Using:&nbsp;
gram concentration = molar concentration × molar mass
conc. Of A in gdm^-3 = 0.055 × [(1 × 2) + (12 × 2) + (16 × 4)]
= 0.055 × 90
= 4.95gdm^-3
======================
No2 solution
2a)
TEST
X + 5cm of distilled water, Divide the solution into 4 portion
OBSERVATION
Salt X is soluble in distilled water
INFERENCE
Salt X is soluble salt
=======================
2bi)
Test
-To the first portion, Add dilute NaOH in drop
-then in excess
OBSERVATION
-White precipitate solution is formed
-The white precipitate is soluble
INFERENCE
Zn^2+ Pb^2+ and AL^3+ are present
=====================
2bii)
TEST
-To the 2nd portion add dilute NH3 solution in drop
-then in excess
OBSERVATION
White gelatinous precipitate is formed which is insoluble in excesa
INFERENCE
Zn^2+,Pb^2+ and Al^3+ are present
======================
2biii)&nbsp;
TEST
To the 3rd portion, Add dilute HCL in drops
-then in excess
-heat the solution
OBSERVATION
White precipitate is formed which Dissolved on heating and re-appears on cooling
INFERENCE
Pb^2+ confirmed
======================
2ci)
TEST
Sample Y + concentrated HNO3
(Cii)&nbsp;
Heat the product formed in (ci)
OBSERVATION
Dirty white curd is formed
===========
It turn to yellow colouration on heating
INFERENCE
Protein is present
====================
2ciii)
TEST
Add concentrated NH3 to the product in (cii)
OBSERVATION
The product in (Cii) turns to orange colour
INFERENCE
Protein is present
=======================
No3
3ai)
i) SO2 change the colour of acidified K2Cr2O7 solution from Orange to green when it is passed through it by changing to Cr2(SO4)3
solution
ii) when zinc dust is added to CuSO4 solution, the solution turn from Blue to white
3aii)
i)Due to the formation of Cr2(SO4)3 solution
ii)Due to the formation of white ZnSO4 since zinc is higher in electrochemical series
3b)
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