Which of the following constitutes an advantage in the use of hard water?

• A. Formation of scum with soap
• B. Furring of kettles
• C. Blockage of water pipes
• D. Formation of strong bones

(a) State three characteristic properties of

(i) electrovalent compounds;

(ii) alpha particles

(iii) catalysts

(b)(i) Write the electronic configuration of silicon (atomic number 14) and state the group to which it belongs in the Periodic Table.

(ii) State the type of chemical bonding between silicon and oxygen in SiO\(_2\)

(iii) A chip used in a microcomputer contains 5.72 x 10\(^{-3}\)g of silicon, calculate the number of silicon atoms in the chip.

[Si = 28; Avogadro constant = 6.02 x 10\(^{23}\) mol\(^{-1}\)]

(c) An element X belongs to the same group as sodium but is more reactive.

(i) Suggest with reason whether X would be a reducing or oxidizing agent.

(ii) What would be a suitable method of storing X in the laboratory?

(iii) Describe briefly what would be observed if a small piece of X were dropped into a trough of cold water which had been coloured with red litmus.

(iv) Write an equation to show how the oxide of X would react with dilute HCI.

(v) Suggest the likely colour of the salts of X

Sugars can be hydrolyzed at room temperature by the action of

• A. mineral acids
• B. strong bases
• C. enzymes
• D. oxidants

A subtance is said to be hygroscopic if it absorbs

• A. water from the atmosphere to form a solution
• B. heat from the surrounding
• C. carbon (IV) oxide from the atmosphere
• D. moisture from the atmosphere without dissolving

A sheet of paper is placed in the path of a beam from a radioactive source. The emissions that pass through the paper consist of

• A. alpha particles and gamma rays
• B. alpha and beta particles
• C. beta particles and gamma rays
• D. alpha particles only

If 10 cm³ of distilled water is added to 10cm³ of an aqueous salt solution, the concentration of the solution

• A. increases
• B. decreases
• C. remains constant
• D. doubles

The atom of an element X combines with aluminium (₁₃AI)?

• A. AIX₂
• B. AI₂X
• C. AI₂X₂
• D. AI₂X₃

A major factor coonsidered in selecting a suitable method for preparing a simple salt is its

• A. crystalline form
• B. melting point
• C. reactivity with dilute acids
• D. solubility in water

A feasible cell was constructed by joining the two half cells below. Cu²⁺ (aq) + 2e^- → Cu(s) Eo = - 0.76 V. What is the standard e.m.f. of the cell?

• A. - 1.1V
• B. - 0.42V
• C. +0.42V
• D. +1.1V

(a)(i) Explain what is meant by acid anhydride and give one example

(ii) State three chemical properties of hydrochloric acid.

(b) Explain each of the following observations:

(i) Tetraoxosulphate (VI) acid can form two types of salts unlike trioxonitrate (V) acid.

(ii) Copper and iron react with concentrated H\(_2\)SO\(_4\) but only one of them reacts with the dilute acid.

(iii) On adding dilute H\(_2\)SO\(_4\) separately to zinc dust and zinc granules of the same mass, the dust produced more vigorous effervescence.

(c)(i) Define activation energy.

(ii) Sketch and label an energy profile diagram for the following reaction: A + B --> C + D; AH = xkJmol\(^{-1}\)

(iii) Explain why the heat of reaction of the mineral acids with sodium hydroxide is constant in value.

(d) Consider the reaction represented by the following equation:

Q\(_{(s)}\) \(\rightleftharpoons\) Q\(_{(l)}\) \(\Delta\) = xkJmol\(^{-1}\)

(i) State with reason which of Q\(_{(s)}\) and O\(_{(J)}\) has the higher entropy.

(ii) What will be the effect of decrease in temperature on the system at equilibrium?