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NECO 2017 Chemistry Practical Solution Answer

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Chemistry-Pract-Answers

Note
Use Your School End Point

1a)
tabulate
Volumeofpipette/baseused=25.0cm3
Indicator used-Phenolphthalein
Burette
Readings

Rough- First,Second,Third
FinalBurette Reading (cm3) |16.00| 
|31.70| 15.65| 31.25|
InitialBurette Reading (cm3)- |0.00| 
|16.00| |0.00| |15.65|
Volumeof acid used (cm3) |16.00| 
|15.70| |15.65| |15.60|
Average titre value
=15.70+15.60+15.65cm^3/3=15.65cm3

1bi)
Concentration of B in moldm^-3
H2C2O4(aq)+2XOH(aq)→ X2C2O4(aq)+2H2O(i) CAVA=nA CBVB=nB
0.08×15.65=1
CB×25/2
CB=2×0.08×15.65/25 =0.100 moldm^-3

1bii)
Molar mass of XOH
Concentration of B in gdm^-3
=1.0×1000/250=4gdm^-3
Therefore,molar mass of XOH
=4gdm^-3 
0.100moldm^-3
=40gmol^-1

1biii)
Relative atomic mass of X
XOH=40
X +16+1=40
X +17=40
X = 40-17
X=23

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Pls Use This No2 Is More Acurate

2ai)
-Test-
X + 5cm distilled water, divided the solution into 4 portion
-Observation-
Effervescence occurs, a reddish brown gas with irritating smell evolved
-Inference-
NO2 gas from NO3 ‎

2bi)‎‎
-Test-
1st portion + NaOH in drop
-Observation-
White ppt formed
-Inference-
Pb2+ or Ca2+

-2bi)-
-Test-
In excess
-Observation-
Soluble in excess
-Inference-
Pb2+ present

2bii)
-Test-
2nd portion + NH3 in drops & dilute NH3 solution 
-Observation-
White ppt formed
-Inference-
Pb2+ or Al3+

-2bii)-
-Test-
In excess
-Observation-
Ppt insoluble in excess
-Inference-
Pb2+

2biii)
-Test-
3rd portion + dil. HCl in drop
-Observation-
White ppt insoluble
-Inference-
Pb2+ present

2ci)
-Test-
Sample Y + concentrated HNO3 2cii) 
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

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3ai)
The colour of k2 Cr2 O7 solution change from orange to green

3aii)
The colour of CuSo4 solution change from blue to colourless

3aii)
i)The solution of K2 Cr2 O7 is reduce due to redox reaction
ii)The copper ions are displaced by Zinc and by displacement
reaction

3b)
CLICK HERE FOR NO3b IMAGE


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