Waec 2018/2019-chemistry Choico
Waec 2018/2019-chemistry Choico
1a)
Volume of pepette = 25.00Cm^2
Indicator Used = Methyl Orange
Tabulate
BURETTE READING|ROUGH|1ST|2ND|3RD|
Final reading Cm^3|25.00|34.00|29.20|24.10|
Initial Reading Cm^3|0.00|10.00|5.00|0.00|
Volume Of Acid Used In Cm^3|25.00|24.00|24.20|24.10|
Average Volume of Acid used =(24.00+24.20+24.10/3)cm^3
=24.10cm^3
1b.(v)
explain why potassium tetraoxomanganate (vii) solution ws acidified with tetraoxo sulphate (vi) acid.
____ KMn04 being a powerful oxidizing agent will oxidize HCL (aq) to chlorine gas hence,the oxidizing power will decrease
b(vi). identify the reducing and oxidizing agent
_____R.A-FeCL2
_____O.A-KMn04
Waec 2018/2019-chemistry Choico
b(vi). why is an indicator not used in the titration?
___this is because KMn04 acts as self indicator since the content of the flask changes from colourless to a permanent pink colour at end point.
Atarp
b(vi) explain what will happen to KMn04 solution if it was not sufficiently acidified?
__ to p[rovide surplus hydrogen to keep the reaction going not interfering with the oxidizing power of KMn04(because it is stable towards oxidation)
b(vii). name two other substances that could be used in the reaction with KMn04 solution instead of FeCL2.
Waec 2018/2019-chemistry Choico
i.( NH4)2S04
ii. SnCL2
b(viii). name two other substances that could be used instead of KMn04.
__ i. K2Cr2O7
__ ii. I2
2a)
-Observation-
part of the C dissolves,colourless filtrate salt
-Inference-
C is a mixture of soluble salt
2bi)
-observation-
white precipitate formed
-Inference-
Cl is present
2bii)
-Observation-
precipitate dissolves
-Inference-
Cl confirmed
2biii)
-Observation-
colourless gas evolved with characteristic choking smell, turns litimus paper blue
-Inference-
Gas is NH3
2c)
-Observation-
Residue dissolves liberating a colourless gas which turns lime water milky
-Inference-
gas is CO2
CO^2-3 present
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Waec 2018/2019-chemistry Choico
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