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2016 NECO GCE CHEMISTRY PRACTICAL QUESTION AND ANSWERS NOW AVAILABLE FOR FREE
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EDUBRAZEE 10:04 Tue, 01 Nov 2016

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WED 2nd November 2016
CHEMISTRY(Alt to practical)2:00pm-4:00pm






(1)
TABULATE
6.09g of Na2CO3 in 500cm^3 H2O
molar mass of HCl=0.20mol/dm^3
Burette|Rough|1|2|3
Final|23.8033.00|45.40|28.50
Initial|0.00|10.50|23.00|6.00
Volume|23.80|22.50|22.40|22.50

(1aii)
Average=(22.50+22.40+22.50)/3
=67.40/3
=22.47cm^3
Equation:
2HCL+Na2CO3->2NaCl+CO2+H2O

(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




=========================


(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

=========================

(3a)
(i) Ammonia (NH3)
(ii) Hydrogen sulphide (H2S)
(iii) carbon monoxide (CO)
(iv) Chlorine (Cl)
(v) oxygen gas (O2)

(3b)
-It turns from green to brown colour
-It turns green from brown colour

(3c)
H2O



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