Q18 of 27 Page 1

Give reasons for the following:

(i) Use of aspartame as an artificial sweetener is limited to cold foods.


(ii) Metal hydroxides are better alternatives than sodium hydrogen carbonate for treatment of acidity.


(iii) Aspirin is used in the prevention of heart attacks.

(i) Aspartame cannot be used for cooking at high temperatures because it is very unstable at high temperatures.


(ii) Excess of sodium hydrogen carbonate can make the stomach very alkaline which in turn triggers the body to produce more acid to cut the alkalinity. Whereas this doesn’t happen when metal hydroxides are used, the pH doesn’t cross neutrality and is a feasible and safe method.


(iii) Heart attacks are mainly caused due to the blocking of blood vessels due to the thickening of the blood or due to cholesterol. Aspirin has anti - clotting action and therefore is used to treat heart attacks.


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16

Which one of the following compounds will undergo faster hydrolysis reaction by SN1 mechanism? Justify your answer.


OR


A compound is formed by the substitution of two chlorine atoms for two hydrogen atoms in propane. Write the structures of the isomers possible. Give the IUPAC name of the isomer which can exhibit enantiomerism.

 17

Complete the following reactions :

 19

(a) Name the branched chain component of starch.

(b) Ribose in RNA and deoxyribose in DNA differ in the structure around which carbon atom?


(c) How many peptide linkages are present in a tripeptide?


OR


Give three reactions of glucose which cannot be explained by its chain structure

 20

The following data were obtained during the first order thermal decomposition of N2O5(g) at a constant volume:

2 N2O5(g)2 N2O4 + O2(G)



Calculate the rate constant.


OR


Two reactions of the same order have equal pre exponential factors but their activation energies differ by 24. 9 kJ mol - 1. Calculate the ratio between the rate constants of these reactions at 27°C. (Gas constant R = 8. 314 JK - 1mol - 1. )