Chemistry 1992 Waec Past Questions and Answers

Question 46 :

• WAEC 1992

(a) Name one metal in each case Which:
(i) exists as a liquid at room temperature,
(ii) can be found in nature in the uncombined state

(b) X and Y are 0.5 mol. dm\(^{-3}\) freshly prepared aqueous solutions of two salts of iron
(II) With excess sodium hydroxide solution, X gave a dirty green precipitate which was not obtained in the case of Y.

Question 47 :

• WAEC 1992

(a) What is meant by the term acid salt? Give one example.
(b) State the reason why an all-glass apparatus must be used for the laboratory preparation of concentrated trioxonitrate (V) acid.

Question 48 :

• WAEC 1992

(a) Name: (i) one structural isomer of glucose.
(ii) the process by which starch is converted to glucose.
(b) The open-chain structure of glucose is shown below.

(a) State the functional groups present in the structure.
(ii) Which of the functional groups would react with warm Fehling's solution?

Question 49 :

• WAEC 1992

(a)(i) State three differences between electrovalent compound and covalent compound.
(ii) Name the type of chemical bonding involved in the formation of ammonium ion from ammonia.

(b)(i) Name the quantum numbers which define an electron within an atom.
(ii) State the orbital in which the fifth electron of an atom is most likely to be found. Sketch the shape of the orbital.
(iii) State the period and the group to which the element boron belongs in the Periodic Table.

(c)(i) What is meant by the entropy of a chemical system?
(ii) Calculate the free energy change for a given reaction at 300 K using the following data obtained for the reaction: \(\Delta\) = -710KJ mol\(^{-1}\); \(\Delta\)S = 0.15 KJ mol\(^{-1}\)K\(^{-1}\)
(iii) From your evaluation in (c)(i) above, state whether the reaction is spontaneous or not at the given temperature. Give reason for your answer.

Question 50 :

• WAEC 1992

(a) Give the products of the following reactions:
(i) hydrolysis of simple proteins.
(ii) alkaline hydrolysis of fats and oils.

(b) A combustion tube was packed with small pieces of broken clay pot and the tube maintained at a temperature of 750K. When the vapour of decane was passed into the tube, the main products included a gaseous hydrocarbon X.
(i) Name the process involved in the reaction. Give its industrial application.
(ii) State the function of the pieces of broken pot in the experiment.
(iii) Give one chemical test to distinguish between X and methane.
(iv) Draw a labelled diagram for the laboratory preparation of X.

(c)(i) State what would be observed if a piece of sodium was added to 10cm\(^3\) of propanol in a beaker. Write an equation for the reaction.
(ii) Give the main product formed when excess acidified potassium heptaoxodichromate (VI) reacts with each of the following: propan-1- ol: propan - 2 -of; State the type of process involved in the reactions.