Chapter 23, Problem 18QAP

Interpretation Introduction

(a)

Interpretation:

The mass percent of C, H and O in starch needs to be determined.

Concept introduction:

Starch is present in plant cells and is a polysaccharide consists of several glucose units.

Mass percent of an atom present in the sample can be determined by dividing mass of atoms present in the monomer to the overall mass of the monomer unit and multiplying the overall result with 100%.

For example, the mass percent of x g of an atom present in the y g of monomer unit can be determined as:

$M\text{ \% = }\left(\frac{x\text{ g}}{y\text{ g}}\right)\times \text{100\%}$

Interpretation Introduction

(b)

Interpretation:

Interpret number of monomer unit of C₆ H₁₀ O₅ in starch needs to be determined.

Concept introduction:

Starch is present in plant cell wall and is a polysaccharide consists of several glucose units in it.

The molar mass of any compound can be calculated by taking sum of molar masses of all the atoms present in that compound.

For a molecular formula of compound C_x H_y O_z, the molar mass can be calculated as follows:

Molar mass of compound = (Number of C) $\times$ (Molar mass of C) + (Number of H) $\times$ (Molar mass of H) + (Number of O) $\times$ (Molar mass of O)