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Chemistry Paper 3


provided with the following: Hydrogen Peroxide labelled solution J. Dilute sulphuric acid labelled solution K. Sodium thiosulphate labelled solution L. Potassium Iodide labelled solution M. Starch solution labelled solution N. Distilled water in a wash bottle. You are required to determine how the rate of reaction of hydrogen peroxide with potassium iodide varies with the concentration of hydrogen peroxide.


Experiment I Label two 200ml or 250ml beakers as beaker 1 and beaker 2. Using a burette, place 25.0cm3 of solution J into beaker 1.Into the same beaker, add 20cm3 of solution K using a 50ml or 100ml measuring cylinder. Shake the contents of beaker 1. Using a 10ml measuring cylinder, place 5cm3 of solution L into beaker 2 followed by 5cm3 of solution M then 2cm3 of solution N. Shake the contents of beaker 2. Pour the contents of beaker 2 into beaker 1 and start a stop clock /watch IMMEDIATELY. Swirl the mixture and let it stand. Note the time taken for the blue colour to appear. Record the time in the space provided for experiment 1 in the table below. Clean beaker 1. Repeat the procedure with volumes of water, solutions J,K,L,M and N as shown in the table for experiments
2 to 5. Complete the table by computing



c) From your graph ,determine the time that would be taken if the contents of beaker 1 were 17.5cm3 water,, 7.5cm3 solution J and 20cm3 solution K. (2mks)

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d) How does the rate of reaction of hydrogen peroxide with potassium iodide vary with the concentration of hydrogen peroxide? (2mks)

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15.5 marks


a) You are provided with solution Q. Carry out the tests below. Record your observations and inferences in the spaces provided. Place 3cm3 of solution Q in a boiling tube. Add 12cm3 of distilled water and shake.


(b) i) Use about 2cm3 portions of diluted solution Q for tests I and II.

I) To the first portion, add drop wise about 1cm3 of sodium hydroxide.


Clean one end of the glass rod thoroughly. Dip the clean end of the glass rod in solution P. Remove the end and heat it in the non-luminous part of a Bunsen burner flame. Note the colour of the flame and record it in table 2. Allow the glass rod to cool for about TWO minutes. Repeat the procedure with solutions R,S and Q and complete 2.

ii) Identify the cation present in solution Q. (1mk) ______________________________________________________________________________ _______________ ______________________________________________________________________________ _______________

15 marks


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

a) Using a metallic spatula, heat about one half of solid T in a Bunsen burner flame.

b) Dissolve the remaining portion of solid T into about 10cm3 of distilled water. Label this solution as solution T. Use this solution for the following tests.

i)To about 2cm3 of solution T, add 3drops of acidified potassium manganate (VII) and warm.

9.5 marks

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