(i) What process leads/tathe formation of K? (ii) Write the formula of K. (iii) Write the structural formula of L and name L. (iv) Name A\(_n\) (v) Write the structure of M and name M.
(b)(i) What are carbohydrates? (ii) Give one example each of a I. monosaccharide; II. disaccharide; III. polysaccharide.
(c) Consider the following structure of a simple sugar :
(i) Which functional group makes the compound a reducing agent? (ii) State what would C = O be observed when I. the compound is mixed with Fehling's solution and boiled; I. few drops of concentrated H\(_2\)SO\(_4\) is added to the sample of the compound. H—C—OH (iii) Write an equation for the reaction in (c)(ii)(II).
(d) A hydrocarbon Z with molecular mass 78 on combustion gave 3.385 g of CO\(_2\) and and 0.692 g of H\(_2\)O. Determine the molecular formula of Z. [ H = 1, C = 12, O = 16]
Explanation
(a)(i) Dehydration (ii) C\(_2H_4\) (iii)
(iv) Polythene/Polythene
(b)(i) Carbohydrates are (naturally occurring) organic compounds containing carbon, hydrogen and oxygen with the hydrogen and oxygen present in the ratio of 2:1 (as in water). (ii)1. Monosaccharide : glucose/fructose 2. Disaccharide: sucrose/lactose/maltose. 3. Polysaccharide : starch/glycogen/cellulose.
(c)(i)
(I) (a) brick red precipitate (b) black/charred mass (of carbon is observed). (iii) C\(_6\)H\(_{12}\)O\(_6\) \(\to\) 6C + 6H\(_2\)O
(d) Mass of hydrogen in Z = \(\frac{12}{8 \times 0.692}\) = 0.077g Mass of carbon in Z = \(\frac{12}{44}\) x 3.385 = 0.923g. C H 0.923 0.077 12 1 0.077 0.077 0.077 0.077 0.077 0.077 Empirical formula of Z = CH (CH)\(_n\) = 78 13\(_n\) = 78 n = \(\frac{78}{13}\) = 6 molecular formula of Z = C\(_6\)H\(_{16}\)
