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WAEC GCE Chemistry Practical Questions and Answers – 2019 Expo
WAEC September 12, 2019 • 1 year ago • 2 Comments

West Africa Examination Council, WAEC GCE Chemistry Practical Questions and Answers for 2019 Second Series WAEC GCE Examination is now available, always subscribe to get the questions and already solved answers by Examrelief before exam.

# 👑 2019 WAEC GCE CHEMISTRY PRACTICAL ANSWERS👑

(1a)
VA=11.30cm³
CA=5.3gldm³
VB=25.0cm³
CB=Ygldm³
HCl(aq)+NaOH(aq)—–>NaCl(aq)+H²O(i)
For acid NA; NB =1;1
(1ai)
Conc of A in moldm-³
=conc of A in gldm-³/molar mass in glmol
=5.3/36.5
HCl=>1+35.5=36.5glmole
=0.145moldm-³
CAVA/CBVB=NA/NB
0.145*11.30/CB*25.0=1/1
1.6385=25CB
CB=1.6385/25
CB=0.06554moldm³
(1aii)
Conc of B in moldm-³=
Conc of A in gldm-³/molar mass in g/mol
0.0655=Yg/dm^3/40
Y=2.62g/dm^3
Molar mass of Y(NaOH)=23+16+1=40g/mol
The value of Y is 2.62g/dm^-3
(1aiii)
HCl+NaOH–>NaCl+H2O
1 mole of HCl gives 1 mole of NaCl
1.6385 mole of HCl would give 1.6385 mole of NaCl
n=CV
=0.145*11.30
=1.6385mole
No of mole =Mass/Molar mass
1.6385=mass/58.5
Molar mass of NaCl=58.5g/mol
Massof NaCl=58.5*1.6385
=95.85
(1b)
(i) Methyl orange
(ii) Orange
===============================
(2)
(2ai)
TEST: E + H2O(stirred)
INFERENCE: E is a mixture of salts
(2aii)
TEST: Residue
INFERENCE: Gas evolved is CO2 from HCO3- or CO3²-
(2aiii)
TEST: residue + HNO3 + H2O
INFERENCE : CO2 gas is evolved from HCO3-or CO3²-
(2aiv)
OBSERVATION: Blue gelatinous ppt soluble in drops. Soluble in excess to give deep blue ppt.
INFERENCE: Cu2+ present
Cu2+ confirmed
(2bi)
INFERENCE : Zn²+, pb²+, Al³+ present
Zn²+, pb²+ present
(2bii)
OBSERVATION: White gelatinous ppt soluble in excess Nh3 solution
INFERENCE: Zn²+, pb²+, Al³+
Zn²+ confirmed
(2biii)
TEST: Portion of filtrate of Ba(NO3)2 + HCL
INFERENCE: SO4²- or CO3²- present.
SO4²- confirmed.
===============================
(3a)
Sucrose + Benedict solution+heat => no colour change
Inference: non reducing sugar present.
Glucose+Benedict solution+heat=> brick red colour formed.
Inference: Reducing sugar like glucose present
(3bi)
(i) potassium iodide
(ii) throsulphate
(3bii)
Starch indicator
(3biii)
(i)before end point – dark color
(ii)at the end point – colourless
(3c)
(i) Soda lime is preferred because it does not attack glass
(ii) Because soda lime is not deliquescent

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