Chemistry Past Questions and Answers

The compound whose formula is written below is a major component of a soft fatty substance:

(a) State the change that would be observed in the physical state of the fatty substance if hydrogen were bubbled through it for long time in the presence of finely divided nickel at about 180\(^o\)C
(c) Determine the amount (in mole) of hydrogen that would be consumed if one mole of the component reacted completely with hydrogen.
(c) State the product of the reaction of the fatty substance with hot concentrated sodium hydroxide solution

(a)(i) Distinguish between a strong acid and a concentrated acid.
(ii) What is meant by amphoteric oxide? Give one example.

(b)(i) Describe the manufacture of tetraoxosulphate (VI) acid by contact process.
(ii) Write one equation each to show the action of tetraoxosulphate (VI) acid respectively as a dehydrating agent and as an oxidizing agent.
(iii) Give the reason why tetraoxosulphate classified as a heavy chemical.

(a)(i) Define the term polymerization.
(ii) List the three conditions required for the polymerization on of ethene.
(iii) State the property which is common to compounds that can be easily polymerized

(b) Write appropriate equations to show how the following can be obtained from propan-1-ol in the labouratory
(i) propene;
(ii) propylmethanoate. State the type of reaction involved in each case.

(c)(i) A compound contains 40.0% carbon, 6.7% hydrogen and 53.3% oxygen. Determine its molecular formula if its molar mass is 180 (H = 1, C = 12, O = 16)
(ii) Explain why ethanoic acid boils at a much higher temperature than butane even though their molar masses almost equal.

(a)(i) What is meant by the rate of a chemical reaction?
(ii) Explain in terms of the vision theory, the effect of temperature increase on reaction rate.

(b) When hydrogen peroxide is exposed to air, it decomposes
(i) Write an equation for the reaction.
(ii) Outline an experiment to illustrate that effect of a named catalyst on the rate of decomposition.
(iii) Sketch an energy profile diagram to show the effect of the catalyst on the reaction rate, given that the reaction is exothermic.
(c)(i) Explain why enthalpy data alone cannot be used to predict whether a reaction can occur spontaneously or not.

The components of universal indicator solution can best be separated by