WAEC Chemistry 2012 Theory — Question 6

Model answer

8(a)(i) I. Biotechnology refers to the use of biological organisms for developing products suitable for human use. II. Biogas refers to a fuel obtained from organic waste using some bacteria as agents through the process of anaerobic decomposition. (ii) Biotechnology plays a key role in waste management; it is harnessed in making substances such as drugs and fertilizers. (b)(i) Yeast should be added to cane sugar juice and then allowed to be for a while. The enzyme sucrose hydrolyses the sucrose in the cane sugar to glucose. The enzyme zymase then ferments the glucose into ethanol. (ii) The by-product is carbon dioxide. (iii) Uses: it is used for preserving soft drinks; it is used as a fire extinguisher; it is used in the Solvay process for the manufacture of NaHCO3 and Na2CO3. (iv) The ethanol from petroleum is said to be non-renewable because the petroleum used for making the ethanol cannot be retrieved once depleted. But sugarcane can be re-planted, from which cane sugar can then be obtained. Thus, the ethanol form cane sugar is said to be renewable. (c) A heavy chemical is produced in large quantity while a fine chemical is produced in small quantity. H2SO4 is an example of a heavy chemical while dyes are examples of fine chemicals. (d) Increasing order of deviation from ideal gas behaviour: O2 < Cl2 < HCl. Deviation from ideal gas behaviour increases as the intermolecular forces increase. The strongest intermolecular forces are found in HCl since it is a polar molecule. Hence, HCl shows the highest deviation from ideal gas behaviour. Both O2 and Cl2 are non-polar; however, the Van der Waals' forces in Cl2 are greater than that of O2 because Cl2 has a greater relative molecular mass.