Chemistry-Pract-Answers
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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2ai)
Tabulate
-Test-
Xn+10cm3of H2O and stirred
-Observation-
Xn dissolves to form a colourless solution
-Inference-
Xn is a soluble salt
2aii)
-Test-
First portion of Xn+ NaOH(aq) in drops,then
in excess
-Observation-
White precipitate which dissolves in excess to give a colourless solution
-Inference-
Zn2+,Pb2+,orAl3+ present
2aii)
-Test-
Second portion of Xn+NH3(aq) in drops,
then in excess
-Observation-
White precipitate in soluble in excess
-Inference-
Pb2+orAl3+ present
2aiii)
-Test-
Third portion of Xn+dil.HCl
-Observation-
White crystalline/chalky precipitate
-Inference-
Pb2+confirmed
2bi)
-Test-
Yn + litmus
-Observation-
Red litmus paper turned blue
-Inference-
Yn is alkaline
2bii)
-Test-
Portion of Yn+conc. HNO3
-Observation-
Yellow colouration
-Inferrence-
Protein present
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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)
DRAW and label a diagram for a set up that can be used to separate suspension of chalk dust in water