Search
Free School Management System
Free School Management System for Kenya

Free School Management System

Learn More

KCSE CLUSTER TESTS 25

Chemistry Paper 3

1.

You are provided with:

- 2M Hydrochloric acid labeled as solution R.

- 0.4M Sodium hydroxide labeled as solution Q.

- 1.06g accurately weighed Anhydrous carbonate X2CO3 labeled solid A.

You are required to determine the relative atomic mass X in one mole of X2CO3.

Procedure

i) Using a clean measuring cylinder, measures 50cm3 of solution R and transfer in 100cm3 plastic beaker.

ii) Add all solid A at once into the contents of the beaker, stir until effervescence stops.

iii) Transfer this solution into a 250ml volumetric flask and add distilled water upto the mark. Label this solution as solution B.

iv) Fill the burette with solution Q.

v) Using a pipette and a pipette filler, place 25cm3 of solution B into conical flask. Add 2 drops of phenolphthalein indicator.

vi) Titrate solution B using solution Q and record the volume of solution Q used.

vii) Repeat the titration two more times and complete the table below.

a) Calculate the average volume of solution Q used.

………………………………………………………………………………………

………………………………………………………………………………………

b) Calculate the number of moles of hydrochloric in 25cm3 of solution B.

………………………………………………………………………………………

………………………………………………………………………………………

c) Calculate the number of moles of hydrochloric acid in 250cm3 of solution B.

………………………………………………………………………………………

………………………………………………………………………………………

d) Number of moles of hydrochloric acid in 50cm3 of solution R.

………………………………………………………………………………………

………………………………………………………………………………………

e) Number of moles of hydrochloric that reacted with the carbonate (solid A).

………………………………………………………………………………………

………………………………………………………………………………………

f) Number of moles of carbonate that reacted with 50cm3 of solution R.

………………………………………………………………………………………

………………………………………………………………………………………

g) Atomic mass of X in one mole of X2CO3 (c=12,o=16)

………………………………………………………………………………………

………………………………………………………………………………………

14 marks

2.

You are provided with solution B(1M HNO3) and solution X (1M NaOH)

You are required to determine the molar heat of solution B Using the procedure below;

Procedure

i) Fill the burette with solution B.

ii) Using a measuring cylinder put 20cm3 of solution X into a plastic cup provided.

iii) Add 4cm3 of solution B from the burette and determine the highest temperature attained.

iv) Continue adding 4cm3 portions of solution B and every time determining the highest temperature attained.

v) Record the highest temperature attained after every addition.

a) Plot a graph of volume of solution B used against highest temperature of solution attained.

b) Determine the volume of solution B that reacts completely with solution X.

…………………………………………………………………………………………………

…………………………………………………………………………………………………

c) From the graph, determine the initial temperature of solution B.

…………………………………………………………………………………………………

…………………………………………………………………………………………………

d) Determine the temperature change when solution X is completely reacted with solution B.

…………………………………………………………………………………………………

…………………………………………………………………………………………………

e) Determine molar heat of solution B used.

…………………………………………………………………………………………………

…………………………………………………………………………………………………

14 marks

3.

You are provided with solid D. Carry out the following tests and write your observations and inferences in the spaces provided.

a) Place a spatula endful of solid D into a clean dry test tube and heat strongly. Test the gases evolved using litmus papers.

b) Place the remaining solid D into a clean boiling tube and add 10cm3 of distilled water. Shake the boiling tube to dissolve the solid. Divide the solution into four portions.

i) To the first portion, add sodium hydroxide solution dropwise till in excess.

ii) To the second portion add ammonia solution dropwise till in excess.

iii) To the third portion, add a few drops of lead (II) nitrate and then filter.

iv) To the fourth portion, add a few drops of acidified barium nitrate solution.

12 marks

Back Top