Chapter 13, Problem 5E

List five common laboratory acids and their uses.

Interpretation Introduction

Interpretation:

Five common laboratory acids and their uses are to be determined.

Concept introduction:

Acids are the ions or molecules capable of losing proton or hydrogen ion $\left({\text{H}}^{+}\right)$ and their pH value is always less than 7. They contain positive metal ions and negative nonmetal ions held together by an ionic bond.

They are sour in taste and are good conductor of electricity.

They are corrosive in nature and produce hydrogen gas when reacted with metals.

There are generally of two types:

Strong acid: They are highly corrosive in nature, completely ionize in a solution, and may cause severe burns on the skin. Examples include hydrochloric acid (HCl), and so on.

Weak acid: They are mild in nature, partially ionize and rarely affect the skin. Examples include acetic acid $\left({\text{CH}}_3\text{COOH}\right)$, and so on.

Answer to Problem 5E

Solution:

Hydrochloric Acid $\left(\text{HCl}\right)$: Its uses are cleaning the metallic surface, purification of food, house cleaning products, and so on.

Sulfuric Acid $\left({\text{H}}_2{\text{SO}}_4\right)$- Its uses are production of fertilizers, dying and pigment, and making of adhesives.

Nitric Acid $\left({\text{HNO}}_3\right)$: Its uses are manufacturing of various fertilizers, explosives, dyes, used in automobiles, carpet, and furniture industries, in cleaning of ornaments/metals.

Phosphoric Acid $\left({\text{H}}_3{\text{PO}}_4\right)$: Its uses are in food industries for flavoring, in fertilizers, for cleaning teeth, house hold detergents and so on.

Acetic Acid $\left({\text{CH}}_3\text{COOH}\right)$: It is used for Vinegar, as a preservative, in rubber industry, in oil and gas industries mainly for oil well stimulation.

Explanation of Solution

Five common acids and their uses as:

i) Hydrochloric Acid $\left(\text{HCl}\right)$

Hydrochloric acid is also known as muriatic acid. This strong acid is highly corrosive in nature and causes severe burns, if it comes in contact with skin. It is a mono protic acid, means it ionizes to give a single proton. It ionizes completely that’s why it is categorized as strong acid.

The reaction is as follows:

$\text{HCl }+{\text{ H}}_2\text{O }\rightleftharpoons {\text{ H}}_3{\text{O}}^{\text{+}}+{\text{ Cl}}^{-}$

Hydrochloric acid is routinely used in laboratories and in manufacturing industries. Some of its uses are as follows:

It effectively cleans the rust present on the metal surface. The reactive chloride ion $\left({\text{Cl}}^{-}\right)$ present in the acid is the key of effectively cleaning the metallic surface.

It used in food industry for preparation and purification of foods. For example, HCl plays an important role in preparation of gelatin, which is used as favoring agent, purification of common salt and so on.

It is used in refining of ores, that is, purification of an impure metal ore. The metals that are noble in nature are dissolved in aqua regia for refining process.

It is used for preparing house cleaning products for example glass cleaners, disinfectant cleaners and so on.

It is also present in our stomach where it performs many functions like killing microorganism etc.

ii) Sulfuric acid $\left({\text{H}}_2{\text{SO}}_4\right)$

Sulfuric acid is also called oil of vitriol or hydrogen sulfate. It is colorless, oily and corrosive acid and is widely used in laboratories and in industries. Sulfuric acid undergoes auto-protolysis, means proton transfer within identical molecules. It gives two proton on ionization.

The reaction is as follows:

$2{\text{H}}_2{\text{SO}}_4\rightleftharpoons {\text{ H}}_3{\text{SO}}_4{}^{\text{+}}{\text{ + HSO}}_4{}^{\text{-}}$

Some of the applications of sulfuric acid are as follows:

It plays an important role in the production of fertilizers like ammonium sulfate

$({\left({\text{NH}}_4\right)}_2{\text{SO}}_4)$ and super phosphate $\left(\text{Ca}{\left({\text{H}}_2{\text{PO}}_4\right)}_2\right)$ is formed when treated with sulfuric

acid.

It also used in dye and pigment industry. Acid dyes are prepared from sulfuric acid. These dyes contain sulphonic groups, which are present as sodium sulfonic salts.

It is used for making of adhesives because the reaction which involves adhesives needs acidic medium. Sulfuric acid not only provides acidic medium to the reaction but also helps to precipitate the desirable product.

It is also used in manufacturing of other acids like hydrochloric acid, nitric acid, and so on.

iii) Nitric acid $\left({\text{HNO}}_3\right)$

Nitric acid is a toxic, corrosive and fuming liquid. It is colorless liquid but sometimes it shows yellow color due to decomposition nitrogen oxides and water.

Nitric acid readily dissociates in water.

The reaction is as follows:

${\text{HNO}}_3(aq){\text{ + H}}_2\text{O(}l\text{) }\to {\text{ H}}_3{\text{O}}^{+}(aq){\text{ + NO}}_3^{-}\left(aq\right)$

The industrial applications of nitric acid are as follows:

It is chiefly used in fertilizer industry for the manufacturing of various fertilizers. Calcium ammonium nitrate $5\text{Ca}{\left({\text{NO}}_3\right)}_2.{\text{NH}}_4{\text{NO}}_3.10{\text{H}}_2\text{O}$ is a widely used fertilizer, commercially known as CAN, is prepared from nitric acid.

It plays major role in the manufacturing of explosives because of versatile functionality of nitro group present in it. It combines with sulfuric acid, generates nitronium ion which rapidly reacts with large number of different organic compounds and is able to form explosives such as tri-nitrotoluene and so on.

It is used in manufacturing of dyes, especially artificial dyes. Nitric acid generally helps manufacture aniline dyes that are chiefly used to dye silk, wood. These aniline dyes also act as a precursor for the formation of other dyes.

It is also used in manufacturing of toluene diisocyanate, a synthetic compound which is used in automobiles, carpet and furniture industries.

It is a component of aqua-regia which is used in cleaning of ornaments/metals.

iv) Phosphoric acid $\left({\text{H}}_3{\text{PO}}_4\right)$

Phosphoric acid is also called an orthophosphoric acid. It is colorless, odorless and a weak acid, which is generally solid at room temperature. It has three ionizable protons. Hence, it ionizes in three different steps, as follows:

$\begin{array}{l}{\text{H}}_3{\text{PO}}_4{\text{ + H}}_2\text{O }\rightleftharpoons {\text{ H}}_3{\text{O}}^{+}{\text{ + H}}_2{\text{PO}}_4{}^{-}\\ {\text{H}}_2{\text{PO}}_4{}^{-}{\text{ + H}}_2\text{O }\rightleftharpoons {\text{ H}}_3{\text{O}}^{+}{\text{ + HPO}}_4{}^{2-}\\ {\text{HPO}}_4{}^{2-}{\text{ + H}}_2\text{O }\rightleftharpoons {\text{ H}}_3{\text{O}}^{+}{\text{+ PO}}_4{}^{3-}\end{array}$

Some industrial applications of phosphoric acid are as follows:

It has non-toxic and mild acidic nature thus, it is used in food industries for flavoring the food or beverages. It generally used in colas and jams to give a tangy flavor.

It is used in the fertilizer industry for manufacturing a number of fertilizers, such as super phosphoric acid is a fertilizer used in feed stock prepared by dehydrating of phosphoric acid.

It is also used as an intermediate in pharmaceutical industries. It is used by dentists for cleaning teeth and also used in anti-nausea medicines.

It is a key ingredient of industrial and household detergents. The phosphate forms complex soluble salts with calcium and magnesium ions present in hard water and prevent them from deposition on the surface to be cleaned.

v) Acetic acid $\left({\text{CH}}_3\text{COOH}\right)$

Acetic acid is named as ethanoic acid. It is a colorless liquid which is sour to taste and has a pungent smell. It is a weak acid and partially ionizes in water.

The reaction is as follows:

${\text{CH}}_3\text{COOH}+{\text{ H}}_2\text{O }\rightleftharpoons {\text{CH}}_3{\text{COO}}^{-}{\text{ + H}}_3{\text{O}}^{+}$

Some industrial applications of acetic acid are as follows:

Vinegar is generally considered an aqueous solution of acetic acid. It is prepared by addition of 10-15% of acetic acid along with small amount of sugar.

It is generally used in pickling of vegetables and other food stuffs in the form of vinegar. This not only provides tangy taste to the foods but also acts as a preservative.

It is a weak acid that offers corrosive properties while remaining environment friendly. The oil and gas industry utilize acetic acid for a number of applications, mainly oil well stimulation.

It is also used in rubber industry as the latex (milky fluid obtained from rubber trees) does not coagulate because of the negative charge present on the surface. Acetic acid neutralizes these charges and helps them to coagulate.