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2014 CHEMISTRY PRACTICALS SPECIMEN & EXPECTED QUESTIONS AND ANSWERS




1. Volumetric Analysis
Plausible formulae to be used
CA=Concentration of an acid
CB=Concentration of a base
VA=volume of an acid
VB=volume of a base
na=number of mole of an acid
nb=number of mole of a base
CAVA/CBVB=na/nb
Mole=Given mass/molar mass
Mole=conc*volume/1000
Given mass/molar mass=conc*volume/1000
Conc in moldm^-3=Conc in gdm^-3/molar mass
% purity=pure/impure*100%
Titration Equation.
2HCL+Na2CO3------>2Nacl+H2O+CO2

Tabulate
Burrette Reading (cm^3)|1st titre|2nd titre|3rd titre
Final burette reading:23.20|33.10|43.10
Initial burette reading:0.00|10.00|20.00
Volume of acid used:23.20|23.10|23.10

Average titre value=23.10+23.10/2
=46.20/2
=23.10cm^3
VA=23.10cm^3.

Quantitative Analysis
Tabulate: Test| Observation| inference
(I)
-Under test: C+H20
-Under observation: Dissolves to give colourless
solution
-Under inference: soluble salt
(II)
-under test:Divide into 2 portions solution C+dil
HNO3+dil AgNO3+Excess
NH3(aq) solution
-under observation:white precipitate,white
precipitate dissolves in
excess ammonia
-under inference:Cl^-1 is present,Cl^-1 is
confirmed
(III)
-under test:Solution C+dil NaOH + Warm
-under observation:Colourless gas evolved with
irritating smell,which
turns moist red litmus paper to blue and form a
white dense fume with
conc HCL
-Under inference:NH3 gas from NH4+
(IV)
-under test:Sol C+ dil Bacl2
-under observation:white precipitate
-under inference:So4^2-,HCO3,CO3^2,SO3^2 are
suspected
(V)
-under test:+dil hcl (excess)
-under observation:white precipitate dissolves
-under inference:SO4^2- is present
(VI)
-under test:sol c+NaOH in drop + in excess
-under observation:white precipitate,precipitate
dissolves/soluble
-under
inference:Ca^2+,Zn^2+,Al^3+,Pb^2,Zn^2+,Al^3+,Pb^2+
present
(VII)
-under test:sol c + NH3(aq)+in drop+in excess
-under observation:white ppt (precipitate),white
precipitate dissolves
-under inference:Al^3+,Pb^2+,Zn^2+,Zn^2+ is
present
Aliter
Cn=NH4cl and 2nSO4
Titration Equation
2HCl+Na2CO3------>2Nacl+H20+CO2(g)
na=2 mole
nb=1 mole
Volume of pipette=25cm^3





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Posted By CHEATMASTER On 02:26 Tue, 01 Apr 2014

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