(a) Give two reasons why luminous flame is not used for heating purposes in the laboratory.    (2mks)

(b) Explain how the hotness of a Bunsen burner flame can be increased..    (1mk)

(a) The diagram below represents a set-up of apparatus used in the electrolysis of lead (II) bromide.

i) Name electrodes C and D                     (1mk)

C…………………………………………..

D…………………………………………..

ii) State and explain the observation made at electrode D         (2mks)

iii) Write the ionic equation for the reaction at electrode C.      (1mk)

iv) State two applications of electrolysis          (2mks)

(b) The table below gives some properties of substances A , B , C and D. Study it and answer the questions that follow.

i) Which particles are responsible for conductivity in substance:         (2mks)

A…………………………………………..

B…………………………………………..

ii) Which substance is likely to be silicon (IV) oxide? Explain      (2mks)

(a)      i) State Hess’ Law                                  (1mk)

ii) Use the equations given below to answer the questions that follow.

I) Draw an energy cycle diagram that links the enthalpy of formation of ethane to combustion of carbon , hydrogen and ethane.                     (1mk)

II) Determine the enthalpy of formation of ethane.           (2mks)

(b) The diagram below shows the set-up of the apparatus used by a student to determine the enthalpy change of combustion of ethanol. The heat produced by burning fuel warms a known mass of water.

Results

Volume of water in the beaker  =  500cm³

Initial temperature of water  =  12⁰C

Final temperature of water  =  31.5⁰C

Mass of ethanol  =  1.50g

Density of water  =  1g/cm³

Specific heat capacity  =  4.2Jkg^-1K^-1

(i) Calculate the heat required to raise the temperature of the water from 12⁰C to 31.5⁰C.      (2mks)

(ii) Find the molar enthalpy of combustion of ethanol.          (2mks)

(C  =  12 , H  =  1 , O  =  16)

(iii) An accurate value for of ethanol is -1368kJmol^-1. State two sources of errors for the low figure obtained.             (2mks)

(iv) Draw an energy level diagram for the combustion of ethanol.        (2mks)

(v) Calculate the heating value of ethanol from the above experiment.         (1mk)

(C  =  12 , H  =  1 , O  =  16)

I Study the scheme below and answer the questions that follow.

(a) Identify substances                                                                     (3mks)

A…………………………………..

B……………………………….....

D………………………………….

(b) State the catalyst necessary for:                                             (2mks)

Step I………………………………………….

Step II………………………………………….

(c) Write down an equation for the reaction represented by step III        (1mk)

(d) Write two balanced chemical equations for the reaction between chlorine gas and:         (2mks)

i) Hot and concentrated sodium hydroxide                     (1mk)

ii) Dilute and cold sodium hydroxide                             (1mk)

II  The diagram below shows an experiment in which Lead (II) nitrate crystals are heated.

(a) Name;                                                     (2mks)

i) Liquid P

ii) Gas Y

(b) Write a balanced chemical equation for the decomposition of Lead (II) nitrate.       (1mk)

(c) Explain how you can distinguish between nitrogen (II) oxide and nitrogen (I) oxide. (2mks)

Study the flow chart below and answer the questions that follow:

(a) Name substance                                                                     (3mks)

X…………………………………..

Q……………………………….....

R………………………………….

(b) Write down an equation for the reaction represented by step III        (1mk)

(c) What are the conditions and reagents required for step?

i)   I                                                                                                (2mks)

Reagent………………………………………….

Condition………………………………………….

ii) IV                                                                                                (2mks)

Reagent………………………………………….

Condition………………………………………….

(d) Name the process represented by:                                              (4mks)

I………………………………………….

II………………………………………….

IV………………………………………….

V…………………………………………...........................

(a) The solubilities of Potassium nitrate and Potassium bromide at different temperatures was determined. The following data was obtained.

i) Draw solubility curves for both salts on the same axis.      (3mks)

ii) From your graph, determine the solubility of each salt at 65⁰C.      (1mk)

iii) 100g of a saturated solution of Potassium nitrate at 70⁰C was cooled to 20⁰C. What mass of the crystals will be crystallized?      (2mks)

(b) Study the flow chart below and answer the questions that follow.

i) Write an equation for the formation of solid A and gas B.         (1mk)

ii) Name.     

Solution C                                                        (1mk)

Solid D                                                              (1mk)

(c) Write the formula of the complex ion in solution E.       (1mk)

Use the information below to answer the questions that follow. The letters are not the actual symbols of the elements.

(a)

i) Write the electronic configuration of the atoms represented by letters T and W.      (1mk)

ii) State the nature of the oxides of the elements represented by Q and U.      (2mks)

(b) Why does the elements represented by the letters T and U have two values of melting points?      (1mk)

(c) Explain the following observations in terms of structure and bonding.

i) There is an increase in boiling point from P to R.         (2mks)

ii) Element S has a high boiling point.      (2mks)

iii) There is a decrease in boiling points from U to W.       (2mks)

(d)

i) Compare the atomic radius of U and V. Explain.       (1mk)

ii) Why is there no ionic radius for W reported in the table?  (1mk)

(a) In an experiment to determine the percentage of oxygen in air , the apparatus below were set-up. Study the set-up and the information provided to answer the questions that follow.

A 500cm³ measuring cylinder K was filled with water and assembled for gas collection. Copper turnings were heated red hot and water was slowly passed into 500cm³ flask H until it reached the 500cm³ mark. A colourless gas was collected in K.

(i) What was the purpose of passing water into flask H?        (1mk)

(ii) What observations were made in the tube I?             (1mk)

(iii) Name one of the gases that is likely to be found in J.        (1mk)

(iv) What was the volume of the gas collected in the measuring cylinder at the end of the experiment?             (1mk)

(v) Calculate the percentage of oxygen in air using the above results.      (2mks)

(b) Study the diagram below and answer the questions that follow.

(i) Give one observation made in the combustion tube after some time.    (1mk)

(ii) Write an equation for the formation of the colourless liquid Y.       (1mk)

(iii) What was the aim of the above experiment as demonstrated in the combustion tube? Explain.       (2mks)

A wooden splint glowing on both ends was fixed as shown in the diagram. The experiment was carried out as indicated.

(a) What will be observed on the glowing splint end A and B if heating is done at the same time.     (1mk)

(b) Explain the observation in (a) above.                    (1mk)

(c) One of the products in this experiment is useful to rocket scientist when going into space. State one way in which the scientist used this product.       (1mk)

The following two tests were carried out on chlorine water contained in two test tubes.

(a) A piece of blue flower was dropped into the first tube. Explain why the flower was bleached.     (2mks)

(b) The second test-tube was corked and exposed to sunlight. After a few days was found to contain a gas that rekindles a glowing splint. Write an equation for the reaction which produced the gas.                    (1mk)