Waec 2016 CHEMISTRY PRACTICAL ALT. B Answers – May/June Expo - Gidifans

You Are Here: Home » Exam - Waec » Waec 2016 CHEMISTRY PRACTICAL ALT. B Answers – May/June Expo - By Mr. Maraj On April 24, 2016 At 8:13 pm

2)
TEST-
i) | F+ Ba (NO2)2 + HNO3 in excess
ii) | F + NaoH(aq) in drops and then in excess
iii) | Mixture + NH3
iv) | Solution From the portion + KSCN

OBSERVATION
i) | white precipitate is formed,precipitate is insoluble in excess HNo3
ii) | white precipitate, precipate insoluble
iii) |white ppt, ppt is insoluble
iv) | blue black/ dark blue /prussian blue precipitated formed

INFERENCE
i) So4^2-Co3^2- or So3^2- present SO4^2- confirmed
ii) Ca^2+ present
iii)Pb^2+ may be present
iv) Pb^2+ confirmed
======================

3a)
i) hydrochloric acid(Hcl) it cannot be collected over water because it is soluble in water
ii)Hydrogen sulphide (H2S) it can be used to dry H2S because it is not alkaline in nature
iii) hydrogen sulphide (H2S) it happens due to reduction reaction
3b)
i) fermentation
ii) decrepitation and decomposition
iii) decomposition
iv) amylases

1)
volume of pipette=25.00Cm^3
indicator used = methal orange
colour change at end point yellow to orange/purple
Tabulate
Burette readin ROUGHcm^3 1STcm^3 2NDcm^3 3RDcm^3
FINAL READING |24.50| |22.50| |22.35| |22.35|
INITIAL READING |0.00| |0.00| |0.00| |0.00| |0.00|
VOLUME OF ACIDE USED |24.50| |22.50| |22.35| |22.35|

Average volume of acide used =2250 + 22.35 + 22.35/3
Average volume of acide used = 67.20/3 =22.40cm^3
1bi)
number of moles =molar conc * volume
volume =22.40cm^3/1000 =0.0224dm^3
number of moles = 0.05 * 0.0224= 0.00112moles
1bii)
if 0.025mole is contained in 250cm^3 of E
there fore
0.0025mole =_ 250cm^3
xmole =_ 25cn^3
0.025*25/250 = 250*x/250
X=0.625/250 =0.0025mole
mole ratio = 0.00112 : 0.0025
=0.00112 * 100000/0.0025 * 100000 =112/250
mole ratio =112 : 250
1c) HxY + xKoH —-> KxY+xH20
1di) basicity of the acide HxY= 2
1dii) HxY could be H2SO4

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20 Comments
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  4. davido says:

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