Chapter 13, Problem 13.142P

(a)

Interpretation Introduction

Interpretation:

The reliability of the measurements that are used to estimate the concentrations of dissolved solids is to be determined.

Concept introduction:

The types of errors are as follows:

1. Systematic error: This error is a part of the experimental setup or faulty devices.

2. Random error: This error occurs always and is due to instruments’ precision.

(b)

Interpretation Introduction

Interpretation:

The types of substances that might have a large error by the conductivity method are to be determined. Also, the reason for this is to be explained.

Concept introduction:

The types of errors are as follows:

1. Systematic error: This error is a part of the experimental setup or faulty devices.

2. Random error: This error occurs always and is due to instruments’ precision.

(c)

Interpretation Introduction

Interpretation:

The mole fraction and molality of ${\text{CaCl}}_2$ are to be calculated.

Concept introduction:

The mole fraction is defined as the ratio of the number of moles of solute to the total number of moles in the mixture. It is represented by $X$.

The formula to calculate the mole fraction is as follows:

  $\text{Mole}\text{fraction}\left(X\right)=\frac{\text{amount}\left(\text{mol}\right)\text{of}\text{solute}}{\left(\begin{array}{l}\text{amount}\left(\text{mol}\right)\text{of}\text{solute}+\\ \text{amount}\left(\text{mol}\right)\text{of}\text{solvent}\end{array}\right)}$        (1)

Molality is the measure of the concentration of solute in the solution. It is the amount of solute that is dissolved in one kilogram of the solvent. It is represented by $m$ and its unit is moles per kilograms. The solute is the substance that is present in a smaller amount and solvent is the substance that is present in a larger amount.

The formula to calculate the molality of the solution is as follows:

  $\text{Molality}=\frac{\text{amount}\left(\text{mol}\right)\text{of}\text{solute}}{\text{mass}\left(\text{kg}\right)\text{of}\text{}\text{solvent}}$        (2)

The $\text{ppm}$ or parts per million is a concentration term that is defined as the mass of any substance divided by the mass of the solution, multiplied by ${10}^6$.