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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

## 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 600cm^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 250cm3 volumetric flask and add distilled water up to the mark
-label this solution W
2. Fill a clean burette with solution W
3. Pipette 25cm^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.

[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 25cm^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 600cm^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 25cm^3 of the solution P from the burette into a clean 100cm^3 glass beaker and place on a white piece of paper with a cross[x] marked on it
2. Add 10cm^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 20cm^3 of solution P form the burette, and add 5cm^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)

[a] plot a graph of 1/t against volume of solution P on the grid provided [3mk]

{b} From the graph
{i} Determine the time taken for the cross to become invisible when 12.5cm^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 5cm^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