2014 CHEMISTRY PRACTICALS SPECIMEN & EXPECTED QUESTIONS AND ANSWERS

By 02:26 Tue, 01 Apr 2014 Comments


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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