2016/17 CHEMISTRY PRATICAL Nov/Dec ans....

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1ai)
Burette reading(cm³): |rough|1|2|3|
Final reading: |23.80|33.00|45.40|28.50|
Initial reading: |00.00|10.50|23.00|6.00|
volume of acide used: |23.80|22.50|22.40|22.50|
1aii)
average volume of acid used = 1st titre 2nd titre
3rd titre/3
average volume = 67.4/3
22.47cm³

1bi)2Hcl+Na2Co3______>Back+Co2+H2o

6.20g=0.5dm^3
Conc. In gram/dm^3 =6.20/0.5=12.4g/dm^3

Vol  b =pippete =25cm^3

Conc. In mol/dm^3 =0.20mol/dm^3

CaVa/CbVb=Na/Nb

0.20*22.4/Cb*25=2/1

4.48/25cb=2/1
50cb=4.48

Fb=4.48/50=0.089mol/Mass

1bii)conc(mol)=conc in g/dm^3 all over molar mass

Na2co3=23*2+12+3*16=106g/dm^3

0.20=conc in g/dm^3 all over 106 

Conc. In g/dm^3=0.20*106

=1.2g/dm^3

1biii}

Mass pure/mass impure *100/1

106/21.2*100

=500g

2a)

i)is a mixture of soluble and insoluble salt

ii)filtrate is acidic

2b)

i)CL- present

ii)OBSERVATION

ppt dissolved

INFERENCE

CL- confirmed

iii)INFERENCE

gas is NH3 from NH4+

2c)

i)the gas is acidic CO2 from CO3^2- or NCO3^-

ii)black reside colourless

filtrate, white ppt

the precipitate dissolved white ppt

iii)the precipitate disolved

2d)

i)

ii)

iii)ethanol

iv)ethylhydrogen tetraoxosulphate(vi)

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3a)
i Ammonia (NH3)
ii Hydrogen sulphide (H2S)
III) carbon monoxide (CO)
Iv) Chlorine (Cl)
V) oxygen gas (O2)
3b)
i)This is because iron has arariable 0xidation
state and it turns from red to green when expose
to air .
FeCL2 is a reducing agent and it is oxidized on
exposure to air.
ii)S02 oxidizes iron in FeCl3 and thereby causes
change in color of the iron compound.
3c)S02.
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