Chapter 13.7, Problem B13.1P

(a)

Interpretation Introduction

Interpretation:

The reason for the addition of cake alum during water purification is to be determined.

Concept introduction:

Alum is a chemical compound, usually a hydrated double sulfate salt of aluminium with the general formula $\text{XAl}{\left({\text{SO}}_4\right)}_2\cdot 12{\text{H}}_2\text{O}$, where $\text{X}$ is any monovalent cation. Double salts are the salts that contain more than one cation and anion. When they are dissolved in water, it dissociates into simple ions. The properties of double salts are not the same as those of its constituents.

(b)

Interpretation Introduction

Interpretation:

The reason for the difficulty in the use of water that contains large amounts of ${\text{Ca}}^{2+}$ and ${\text{Mg}}^{2+}$ for cleaning is to be determined.

Concept introduction:

Water that contains high mineral content is known as hard water. It is formed when water percolates through deposits of chalk, gypsum that is made up of calcium and magnesium carbonates, bicarbonates and sulfates.

(c)

Interpretation Introduction

Interpretation:

The meaning of “reverse” in reverse osmosis is to be determined.

Concept introduction:

The osmotic pressure is defined as the measure of the tendency of a solution to take in pure solvent via osmosis. It is defined as the minimum pressure that is to be applied to the solution to prevent the inward flow of the pure solvent across the semipermeable membrane. Osmosis occurs when two solutions have different concentrations of solute and are separated by a semipermeable membrane.

(d)

Interpretation Introduction

Interpretation:

The reason for the use of ozone instead of chlorine as a disinfectant is to be determined.

Concept introduction:

Disinfectants are antimicrobial agents that are applied to the non-living things so as to destroy microorganisms. These are different from other antimicrobial agents such as antibiotics and antiseptics because these are applied to living beings. Bleach, alcohol, thymol, and chloramine are some of the examples of disinfectants.

(e)

Interpretation Introduction

Interpretation:

The regeneration of resin by the passage of a saturated $\text{NaCl}$ solution through a “spent” ion-exchange resin is to be explained.

Concept introduction:

An ion-exchange resin is a polymer or resin that acts as a medium for ion-exchange. It is an insoluble matrix that is generally in the form of microbeads. The ion-exchange resins are used in different separation, purification, and decontamination processes. The most common examples are water softening and water purification.