NECO GCE CHEMISTRY PRACTICAL ANSWERS

CHEMISTRY PRACTICAL ANSWERS
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PLEASE GO THROUGH YOUR WORK AND CORRECT THE NECESSARY ONES..

TABULATE
1ai)
Burette reading(cm³): |rough|1|2|3|
Final reading: |23.80|33.00|45.40|28.50|
Initial reading: |00.00|10.50|23.00|6.00|
volume of acide used: |23.80|22.50|22.40|22.50|

1aii)
average volume of acid used = 1st titre+2nd titre+3rd titre/3
average volume = 67.4/3
22.47cm³

1bi)
2Hcl+Na2Co3 -> Back+Co2+H2o 6.20g=0.5dm^3
Conc. In gram/dm^3 =6.20/0.5=12.4g/
dm^3
Vol of b = pippete =25cm^3
Conc. In mol/dm^3 =0.20mol/dm^3
CaVa/CbVb=Na/Nb 0.20*22.4/Cb*25=2/1
4.48/25cb=2/1
50cb=4.48
Fb=4.48/50=0.089mol/dm^3

1bii)
conc(mol)=conc in g/dm^3 all over molar mass
Na2co3=23*2+12+3*16=106g/dm^3
0.20=conc in g/dm^3 all over 106
Conc. In g/dm^3=0.20*106
=1.2g/dm^3

1biii)
Mass pure/mass impure *100/1
106/21.2*100
=500g
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2ai)
Inference: An endothermic reaction
contains soluble and insoluble salts

2aii)
inference: Filterate is acidic

2bi) Ca^2+,Zn^2+,Pb

2bii)
Observation: White ppt,soluble in excess
Inference:Zn2+ confirmed

2biii)
Observation: White ppt insoluble in excess, Inference:NH3 from NH4^+

2ci)
Inference: CO2 from CO3^-

2cii) Inference: Zn^2+,Pb^2+,Al^2+
suspected

2ciii) Observation: white precipitate soluble in excess, Inference: Zn^2+
confirmed

2d)
i)
ii)
iii)ethanol
iv)ethylhydrogen tetraoxosulphate(vi)
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3a)
i)NH3 has the highest rate of diffusion
ii)H2S smells like rotten egg
iii)CO forms carboxyhaemoglobin
iv)CL2 has a greenish-yellow colour

3bi)
FeCL2(aq)+O2 ==> 2FeO(aq)+CL2(g)
It is observed that iron(II)oxide is formed and chlorine gas is liberated

3bii)
SO4(g)+2FeCL3(aq)+2H20(l) —> 2FeCL2(aq)+H2SO4(aq)+2HCL(aq)
It reduces brown iron(ii)chloride sodium to green iron(ii)chloride solution and the sulphur(iv)oxide is oxidized to tetraoxosulphate(vi) acid.

3c)oxides of hydrogen (H2O)
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