CHEMISTRY PRACTICAL QUESTIONS AND ANSWERS NOW READY FOR 31 MAY 2016 10:00am-12:00pm

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1) volume of pipette used =25.0cm^3

indicator used =methyl orange

burette reading|rough| 21.50|0.00|21.50|

final burette readings (cm^3)|1st|21.20| 0.00. 21.20|

initial burette reading(cm^3)|2nd|31.20|10.00| 21.20|

volume of a used (cm^3)|3rd|41.20|20.00|21.20|

average volume of a used =(21.20+21.20+21.20)cm^3/3 =63.60cm^3/3 =21.20cm^3

equation of the reaction

H2SO4(aq) + 2NaoH(aq)+2H2O(s) nA=1,nB=2

A=4.90gldm^3 H2SO4

molar mass H2SO4 =(1*2)+32+(16*4) =2+32+64 =98gmol^-1

molar conc A=mass con A/molar mass A =4.90gldm^3/98glmol =0.05moldm^3

CAVA/CBVB=nA/nB 0.05moldm^3*21.20cm^3/CB*25.0cm^3=1/2

0.05moldm^3*21.20*2=CB*25.0

CB=0.05molldm^3*21.20*2/25.0

CB=0.0848moldm^3 in mass conc B =Molar B*MolarBmass

B=NaoH =23+16+1 =40gmol-^3

mass conc B =0.0848moldm^3 * 40gmol mass con B = 3.392gldm^3

% mass of impusx 100%/total mass of implusty mass of implus =(4.0-3.392)gldm^3 =0.608gldm^3

%impurity =0.608gldm^3*100%/4.0gldm^3 =15.2%

2ai) Observation:The salt sample dissolves completely Inference:C is a mixture of soluble salts

2aii) Observation:White precipitate insoluble in excess NaOH(aq) Inference:Ca^2+ present

2aiii) Observation:No visible reaction Inference:Ca^2+ is present

2aiv) Observation:Brownish fume is produced Inference:NO2(g) form, NO3^- present

2av) Observation:Formation of brown gas which forms a ring junction with FeSO4 Inference:NO2 form, NO3^- confirmed

2bi) Observation:D dissolves completely. Formation of dirty green precipitate insoluble in excess NaOH(aq) Inference:D is soluble in salt, Fe^2+ present

2bii) Observation:Formation of a white precipitate.precipitate remains insoluble in HCl(aq) Inference:SO3^2-,CO3^2-,SO4^2- present,SO4^2- confirmed

3ai) Drawing lebel

-lid

-sticky tape(to hold paper)

-choroatographic paper

-gas jar

-applied spot of solute mixture

-ion

3aii) principle of dillution, C1 V1=C2 V2 2.0molldm^3*40

3bi) ethanol---->ethanoic (acid)---->trioxonotrate(v) (acid)

3bii) indicators are used to determine the end point of the reaction and to test the acidity or alkalinity of a solution

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Article Name	CHEMISTRY PRACTICAL QUESTIONS AND ANSWERS NOW READY FOR 31 MAY 2016 10:00am-12:00pm
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Author Name	Head Admin
Published On	5/27/2016
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