Chapter 13, Problem 13.128P

(a)

Interpretation Introduction

Interpretation:

The molar mass of the compound is to be calculated.

Concept introduction:

The freezing point is the temperature at which both the solid and liquid phases coexist in equilibrium. It is the temperature at which the vapor pressure of the substance in the liquid state becomes equal to the vapor pressure in a solid state.

The formula to calculate the change in freezing point is as follows:

  $\Delta T_{\text{f}}=i{k}_{\text{f}}m$        (1)

Here,

$\Delta T_{\text{f}}$ is the change in freezing point.

$i$ is van’t Hoff factor.

$k_{\text{f}}$ is the freezing point depression constant.

$m$ is the molality of the solution.

(b)

Interpretation Introduction

Interpretation:

The empirical and the molecular formula of the compound are to be determined.

Concept introduction:

An empirical formula gives the simplest whole number ratio of atoms of each element present in a molecule. The molecular formula tells the exact number of atoms of each element present in a molecule.

(c)

Interpretation Introduction

Interpretation:

The Lewis structures for the compound that forms hydrogen bonds and one that does not form hydrogen bonds are to be drawn.

Concept introduction:

Lewis structure is basically a simplified representation of the structure of any molecule or atom. Lewis structure shows the bonding between the atoms and the lone pairs of electrons as dot.

The steps to draw the Lewis structure of any molecule are as follows:

1. Write the letter symbol for each element present in the compound and draw the skeletal structure. Generally, the least electronegative element is considered as the central element.

2. Count the total number of valence electrons in the molecule. In case of charged molecules subtract the positive charge from the total number of valence electrons and add the negative charge to the total number of valence electrons.

3. Assign two electrons between two atoms and join them via a single bond. Place the remaining valence electrons as lone pairs such that octet of each element is achieved. Use multiple bonds to complete the octet.