Waec 2018/2019-chemistry pratical

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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