NABTEB 2016 100% CORRECT CHEMISTRY PRACTICAL QUESTIONS AND ANSWERS

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1a)

volume of pipette

Vf=25.00cm^3

 

1aii)

1)TABLE OF RESULT

Burette Readings (cm^3),

Rough Titration,

First Titration,

second Titration,

Burette Reading |final(cm^3)|

Initial(cm^3)|volume of acide (cm^3)|

 

Rough tire|24.80|0.00|24.80|

1st titre|49.30|24.80|24.50|

2nd titre|24.40|0.00|24.40

Average Volume of Acid Used

VE=24.50+24.40/2

VE=24.45cm^3

 

1bi)

con of f(moldm^3) =mass

conc/molar mass

molar mass NaOH

=23+16+1=40glmol conc of F=3.90/40=0.098moldm^3

 

1bii)

using Ce Ve/Cf Vf =Ne/Nf

Ce*24.45/0.098*25=1/2

conc of E

=0.098*25/24.45*2=0.050moldm^3

 

1biii)

conc of E in gldm^3=2.45*100/500=4.90gdm^3

 

1bvi)

molar mass of H2X=mass

conc/molar conc

=4.90/0.050 =98gmol^1

 

2a)

TABULATE under TEST

2ai)sample G + H20 +

filtration

 

2aii)filtrate + litmus paper

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2bi)1st portion filtrate +

AgNO3 + dil.HNO3

2bii)mixture in (2bi) + NH

3(aq)

2biii)2nd portion filtrate +

NaOH(aq) + heat

2c)residue + dil.HCl + heat

2di)solution from (2c) +

drops NaOH and in excess

2dii)solution from (2c) + NH3(aq)

under OBSERVATION

 

2ai)sample G solube partially to give a colourless filtrate

2aii)turns red litmus paper to blue

 

2bi)white ppt is formed

2bii)the precipitate dissolve in excess NH3(aq)

 

2biii) a colourless gas with irritating smell which form a white dense fume with conc HCl stopper

 

2c)dissolve with effervescerence of

colourless,odourless,acid gas which turn lime water milky

 

2di)white gelatinous ppt

soluble in excess NaOH(aq)

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2dii)white gelatinous ppt is

formed which dissolve in

excess NH3(aq)

under INFERENCE

2ai)sample G is a mixture of soluble and insoluble salts

 

2aii)basic solution

2bi)Cl^- present

2bii)Cl^- confirmed

2biii)NH3 from NH^+4

present

2c)CO^-2 gas from CO3^2 or HCO^-3

2di)Pb^2+ Zn^2+ or Al^3+ present

2dii)Zn^2+ confirmed

 

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3a)

i)copper trioxocarbonate(vi)

CuCO3

ii)carbondioxide(CO2) gas

iii)copper (Cu)

 

3b)

CuCO3(s) heat—->CuO(s) + CO 2(g)

 

3c)

TEST=drops of sodium

hydroxide plus the solution OBSERVATION=blue gelatinous precipitate which

is not dissolve in excess

sodium hydroxide

 

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