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?NECO 2017 CHEMISTRY PRACTICAL ANSWERS?
100% VERIFIED CHEMISTRY PRACTICAL ANSWERS
Note: Candidates are strongly advised to check which size of pipette used by their school.
We make used of 25cm³ in the solution
If your school used 20cm³, all you need do is use it in place of 25cm³ anywhere we used it and calculate accordingly
NOTE:ALWAYS MAKE USE OF YOUR SCHOOL ENDS POINT
1) Volume of Pipette used 25.0cm^3
Titration | Rough | First | Second | Third
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
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
gram concentration = molar concentration * molar mass
conc. Of A in gdm^-3 = 0.055 * [(1*2) + (12*2) + (16*4)]
= 0.055 * 90
X + 5cm of distilled water, Divide the solution into 4 portion
Salt X is soluble in distilled water
Salt X is soluble salt
-To the first portion, Add dilute NaOH in drop
-then in excess
-White precipitate solution is formed
-The white precipitate is soluble
Zn^2+ Pb^2+ and AL^3+ are present
-To the 2nd portion add dilute NH3 solution in drop
-then in excess
White gelatinous precipitate is formed which is insoluble in excesa
Zn^2+,Pb^2+ and Al^3+ are present
To the 3rd portion, Add dilute HCL in drops
-then in excesa
-heat the solution
White precipitate is formed which Dissolved on heating and re-appears on cooling
Sample Y + concentrated HNO3
Heat the product formed in (ci)
Dirty white curd is formed
It turn to yellow colouration on heating
Protein is present
Add concentrated NH3 to the product in (cii)
The product in (Cii) turns to orange colour
Protein is present
S02 changes the colour of acidified K2Cr2O7 solution from orage to green when it is passed through it by changing it to Cr2(So4)3 solution
When Zinc dust is added to CUSO solution, the solution turns from blue to white.
Due to the formation of Cr2(So403 solution.
Due to the formation of white ZnSo4 since Zn is higher in the electrochemical series
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