Using energy cycle diagram , calculate the enthalpy of formation of ethane from the information given below.         (3mks)

Chlorine and Iodine are elements in the same group in the periodic table.

(a) What observation would be made if chlorine gas is bubbled through aqueous sodium iodine? Explain using an ionic equation.           (2mks)

(b) Using the equation in (a) above , identify and explain the reducing agent.        (1mk)

Starting with solid lead (II) carbonate , briefly describe how a sample of lead (II) chloride can be prepared.        (3mks)

The table below shows the standard reduction potentials for four half-cells. Study it and answer the questions that follow (letters are not the actual symbols for element)

i) Identify the strongest reducing agent. Explain        (1mk)

ii) Write the equation for the reaction which takes place when solid G is added to a solution containing H²⁺ ions.          (1mk)

iii) Calculate the E⁰ value for the reaction in (ii) above.         (1mk)

20cm³ of a dibasic acid requires 25cm³ of 0.1M NaOH for complete neutralization.

(a) How many moles of sodium hydroxide reacted with the dibasic acid?      (1mk)

(b) Calculate the concentration of the dibasic acid in moles per litre.       (2mks)

A radioactive substance weighing M kg took 1900 years for the original mass to reduce to 15kg. Given that half-life of the radioactive substance is 380 years:

(a) Determine the original mass of the radioactive substance.         (2mks)

(b) State two uses of radioactivity in medicine.             (1mk)

Study the diagram below:

(a) State the observations made at I and II.                  (1mk)

(b) Write the equations to show the reaction in II if dry Sulphur (IV) oxide was used in place of dry chlorine.          (2mks)

The table below shows properties of some elements A , B , C and D which belong to the same period of the periodic table. The letters do not represent the actual symbols of the elements.

(a) Arrange the elements in the order they would appear in the period. Give a reason.     (2mks)

(b) Select the metallic element which is better conductor of electricity. Give a reason.    (1mk)

The table below shows the solubility of a salt at various temperatures.

(a) Define the term Fractional crystallization                          (1mk)

 (b)  Calculate the mass of salt formed when 20g of a saturated solution of the salt at 0⁰C is placed in a water bath maintained at 100⁰C.           (2mks)

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

(a) Identify

i) Solid X                                     (1/2mk)

ii) Process W                                 (1/2mk)

(b) Write an equation for the reaction in step II                        (1mk)

(c) Explain why copper is suitable in making soldering equipment.      (1mk)