(a)(i) Give one major use of alkenes. (ii) Name the simplest alkane that exhibits structural isomerism (iii) Determine the molar mass of an alkane that is represented as C\(_x\)F\(_{22}\). [H = 1, C = 12] (iv) List two types of chemical reactions which the alkenes and alkynes undergo.
(b)(i) State the type of reaction involved in the conversion of palm oil to margarine. (ii) Give the reason why the palm oil for manufacturing margarine is first treated activated charcoal (iii) What is commonly used to catalyse the conversion of vegetable oils to margarine?
(c)(i) Name the class of organic compounds to which oils belong. (ii) Describe briefly procedure for the manufacture of soap from vegetable oils (iii) Explain why the presence of calcium ions in domestic water supply wastes soap.
Explanation
(a)(i) They are used for fuels (ii) Butane (iii) General formula C\(_n\)H\(_{2n + 2}\) or C\(_x\)H\(_{2x + 2}\) 2x + 2 = 22; x = 222 x = 10; Formula is C\(_{10}\)H\(_{22}\) and Molar mass = (12 x 10) + (1 x 22) = 142g (iv) Addition reaction (2) combustion
(b)(i) Hydrogenation or addition of hydrogen (ii) To decolorize or bleach it (iii) Finely divided nickel
(c)(i) Alkanoates (ii) Vegetable oils and caustic soda or potash solution is then added later to salt out or separate the soap (from the glycerol) (iii) The presence of Ca\(^{2+}\) in water causes hardness. The ion react with soap to form a precipitate (scum) until all the Ca\(^{2+}\) is removed. The soap does not form a lather and is thus wasted
