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Form 4 Chemistry Paper 3 End of Term 2 Exams 2021

Class: Form 4

Subject: Chemistry

Level: High School

Exam Category: Form 4 End Term 2 Exams

Document Type: Pdf

    

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Exam Summary


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CHEMISTRY
PAPER 3
END OF TERM 2 EXAM 2021

QUESTION 1
• You are provided with solution K and L
• Solution K is 1M #H_2SO_4#
• Solution L contains 8.7g of the hydroxide of metal M {with formulae MOH] in 600#cm^3# of the solution
• You are required to carry out the experiment to determine;
i. Concentration of solution L
ii. R.A.M of metal M
Procedure
1. Measure 75cm3 of solution K and put into a clean 250#cm3# volumetric flask and add distilled water up to the mark
-label this solution W
2. Fill a clean burette with solution W
3. Pipette 25#cm^3# of solution L into a clean conical flask and add 2 drops of phenolphthalein indicator
4. Titrate the solution W in the burette against solution L in the conical flask and record the results in the table below
5. Repeat {3} and {4} above as you fill the table below.

Capture1.JPG [4mks]
{a} Calculate the;
{i} Average volume of solution W used [1mk]


{ii} Concentration of solution W [1mk]


{iii} Number of moles of solution W that reacted with each 25#cm^3# portion of solution L {2mks]


{b} Calculate the;
{i} Number of moles of the metal hydroxide {MOH} in solution L that reacted with each portion of solution W [2mks]


{ii} Concentration of solution L [1mk]


{iii} Number of moles of the metal hydroxide [MOH]in 600#cm^3# of solution L [2mks]


{iv} R.A.M of metal M [2mks]
[0=16, H=1]

QUESTION 2
You are provided with solution N and P
• Solution N is 2M HCl
• Solution P is 0.16M sodium thiosulphate
• You are required to carry out the experiment below to determine how concentration affects the rate of reaction between HCl and sodium thiosulphate solutions

PROCEDURE

1. Fill a clean burette with solution P.
Measure 25#cm^3# of the solution P from the burette into a clean 100#cm^3# glass beaker and place on a white piece of paper with a cross[x] marked on it
2. Add 10#cm^3# of solution N into it and immediately start a stop watch and note the time taken for the cross beneath the mixture to become invisible
3. Clean the #100cm^3# beaker and measure into it 20#cm^3# of solution P form the burette, and add 5#cm^3# of distilled water into the solution solution
4. Repeat step [2] above and note the time taken for the cross to become invisible
5. Repeat the experiment using volumes indicated on the table below and as you record the results (4mks)
Capture2.JPG
[a] plot a graph of #1/t# against volume of solution P on the grid provided [3mk]
Capture3.JPG
{b} From the graph
{i} Determine the time taken for the cross to become invisible when 12.5#cm^3# of solution P is used [2mks]


{ii} Explain the effect of concentration on the rate of reaction between HCl and sodium thiosulphate solution [2mks]


QUESTION 3
• You are provided with solids Q and R
• You are required to carry out the tests below as you record your observations and inferences
(i) SOLID Q
-Add about 5#cm^3# of distilled water to solid Q, shake the mixture thoroughly for a while and then filter it
NOTE: Retain both the filtrate and the residue for the tests below
Capture4.JPG
Capture5.JPG
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