Waec Chemistry 2001 Past Questions and Answers

Question 51:

• WAEC 2001

CuSO₄ 5H₂O can be obtained from an aqueous solution of copper (ll) tetraoxosulphate (VI) by

A. Evaporation to dryness
B. Using chromatography
C. Precipitation
D. Crystallization

Question 52:

• WAEC 2001

Which of the compounds will leave a metal residue when heated?

A. Cu(NO ₃ )₂
B. AgNO₃
C. K₂CO₃
D. CaCO₃

Question 53:

• WAEC 2001

A visible change is observed when a strip of iron is placed in an aqueous solution of

A. FeSO₄
B. ZnSO₄
C. CuSO₄
D. MgSO₄

Question 54:

• WAEC 2001

(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

Question 55:

• WAEC 2001

(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?