Chapter 4, Problem 4.144P

(a)

Interpretation Introduction

Interpretation:

The moles of iodate form per mole of thyroxine are to be calculated.

Concept introduction:

Stoichiometry of a reaction is utilized to determine the amount of any species in the reaction by the relationship between the reactants and products.

Consider the general reaction,

  $\text{A}+2\text{B}\to 3\text{C}$

One mole of $\text{A}$ reacts with two moles of $\text{B}$ to produce three moles of $\text{C}$. The stoichiometric ratio between A and B is 1:2, the stoichiometric ratio between A and C is 1:3 and the stoichiometric ratio between B and C is 2:3.

(b)

Interpretation Introduction

Interpretation:

The oxidizing and reducing agents in the reaction are to be identified. Also, the number of moles of iodine produced per mole of thyroxine is to be calculated.

Concept introduction:

A redox reaction is a type of reaction that involves the change in oxidation number of a molecule, atom or ion changes due to the transfer of an electron from one species to another.

An oxidizing agent is a substance that oxidizes another species and itself gets reduced in a chemical reaction. A reducing agent is the one that reduces another species and itself gets oxidized in a chemical reaction.

(c)

Interpretation Introduction

Interpretation:

The mass percent of thyroxine in the thyroid extract is to be calculated.

Concept introduction:

Mass percent is employed to determine the concentration of one compound in a mixture of the compound. The formula to calculate mass percent is as follows:

  $\text{Mass percent of compound}=\left(\frac{\text{mass of the compound}}{\text{mass of mixture}}\right)100$

The expression to calculate the amount of compound in moles when molarity of solution and volume of solution is given is as follows:

  $\text{Moles of solute}=\left(\text{volume of solution}\right)\left(\text{molarity of solution}\right)$        (3)