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100% Real Waec Gce 2015 Chemistry Practical Answers.




1a)
i)
Mass concentration of B=3.95/750*1000
=5.2g/dm
VA=22.70cm^3
VB=25.0cm^3

ii)
Concentration of B in mol/dm^3
=Concentration in g/dm^3/Molar mass in g/
mol
Molar mass of Na2CO3
=(23*2)+(12)+(16*3)
=46+12+48
=106g/mol
Concentration in mol/dm^3=5.27/106
=0.0497mol/dm^3

iii)
CAVA/CBVB=nA/nB
(CA*22.70)/(0.0497*25)=1/1
CA=(0.0497*25*1)/22.70*1)
CA=0.0548mol/dm^3

iv)
CA=concentration in g/dm/molar mass
Molar mass of A=H2SO4
=(1*2)+32+(16*4)
=2+32+64
=98g/mol
0.0548=concentration in g/dm^3/98
Concentration of A in g/dm^3=0.0548*98
=5.37g/dm^3

(1b)
0.0548=mole/1
mole=0.0548mol
0.0548=x/6.02*10^23
x=0.0548*6.02*10^23
x=3.3*10^22

(1c)
Methyl orange: This is because it is between
strong
acid and weak base




(2)
(a)Inference: C is a soluble salt

(bi) Observation: A gas with irritating smell is
formed

(bii) Observation: A dense white fume of
NH4Cl is
formed

(c)Observation:-Soluble in excess

(d)Observation: A gas that turns lime water
milky and
red litmus paper to blue

(ei) Inference: Ca^2a+ -present

(eii) Observation: White precipitate is
formed,insoluble

(fi) Filtrate->CaSO4

(fii) residue->CaCO3

(3ai)
Q->H2
R->CuO
X->H2O
Y->Cu

(3aii)
Blue to Black

(3aiii)
X is serves as cooling

(3b)
-Ammonia
-Hydrogen sulphide
-Chlorine
-Ammonia
-Bromine

(3c)
-Tomeasure a known volume of gas
-To keep clean substance
-To deliver a substance
-To keep a substance dry



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