a. A structure for the disaccharide maltose (C12H22O11) is given below - VCE - SSCE Chemistry - Question 4 - 2007 - Paper 1

The balanced equation for the combustion of maltose can be represented as follows:

$C_{12}H_{22}O_{11} + 12 O_{2} \rightarrow 12 CO_{2} + 11 H_{2}O$

The ΔH value for the combustion of one mole of maltose can be estimated around -5632 kJ. This is calculated by recognizing that the combustion of glucose (a product of maltose hydrolysis) typically releases about 2816 kJ per mole. Since hydrolysis yields two glucose molecules, the value is doubled, leading to the approximation of -5632 kJ, considering complete combustion of all glucose products.

The structural formula for glycerol (C3H8O3) is drawn as:

   H   H   H
   |   |   |
H—C—C—C—OH
   |   |   |
   OH  OH  H

This representation shows all bonds including the hydroxyl (OH) groups.

The balanced equation for the formation of methyl stearate from methanol and stearic acid can be represented as:

$C_{18}H_{36}O_{2} + CH_{3}OH \rightarrow C_{18}H_{36}O_{2}^{*} + H_{2}O$

Here, C18H36O2* represents methyl stearate.

In the structure of methyl stearate, the ester functional group can be identified as:

   O
   ||
H—C—C—C—C—...—O—CH3 

In this structure, the bond between the carbonyl (C=O) and the oxygen (–O–) adjacent to the methyl group (–O–CH3) is the complete ester group.

Lecithin is a phospholipid containing both hydrophilic (water-attracting) and hydrophobic (water-repelling) regions. Its structure includes a hydrophilic phosphate head and two hydrophobic fatty acid tails. This unique amphiphilic nature allows lecithin to interact with both water and oil, stabilizing emulsions by reducing surface tension and preventing separation.