Chapter 13, Problem 7E

List four common laboratory bases and their uses.

Interpretation Introduction

Interpretation:

Four common laboratory bases and their uses are to be determined.

Concept Introduction:

A base is a chemical species that donates electrons, accepts protons or releases hydroxide ions $\left({\text{OH}}^{-}\right)$ in solutions. Bases display certain characteristics properties that can be used to identify them. They tend to be slippery to touch, taste bitter, readily react with acids to form salts and catalyze certain reactions.

These particular substances produce hydroxide ions $\left({\text{OH}}^{-}\right)$ and thus, are also classified as Arrhenius bases.

Bases react with acids to form salt and water.

Base turns litmus paper blue.

Toxins and alkoxides are bases that are carcinogenic in nature and cause a number of side-effects, if consumed.

Some common bases are sodium hydroxide, potassium hydroxide, sodium bicarbonate and ammonia.

Sodium bicarbonate is commonly known as baking soda, having chemical formula $\left({\text{NaHCO}}_3\right)$. It is a salt composed of sodium cation $\left({\text{Na}}^{+}\right)$ and a bicarbonate anion $\left({\text{HCO}}_3{}^{-}\right)$. It appears as a white crystalline, odorless solid having pH nearly 8-8.5, which indicates that it is an alkaline salt and has a bitter taste.

Calcium carbonate is the principle component of limestone. It is also found in pearls, shells in the marine organisms, and is commonly used as chalk in classrooms. It is a salt of the bivalent calcium cation $\left({\text{Ca}}^{2+}\right)$ and the bi-dentate carbonate anion $\left({\text{CO}}_3{}^{2-}\right)$. It is an odorless, fine crystalline powder and has a wide range of applications.

Ammonia is a compound of nitrogen and hydrogen having chemical formula $\left({\text{NH}}_3\right)$. It is a colorless gas, has a pungent odor and causes irritation to eyes, nose, throat, and skin. Aqueous form of ammonia is referred to as ammonium hydroxide.

It is popularly known as caustic soda, having molecular formula $\left(\text{NaOH}\right)$. It is a white solid compound, which consists of sodium cations $\left({\text{Na}}^{+}\right)$ and hydroxide anions $\left({\text{OH}}^{-}\right)$. It is highly soluble in water and readily absorbs moisture from the air.

Answer to Problem 7E

Solution:

Sodium Bicarbonate $\left({\text{NaHCO}}_3\right)$

Calcium Carbonate $\left({\text{CaCO}}_3\right)$

Ammonia $\left({\text{NH}}_3\right)$

Sodium Hydroxide (NaOH)

Explanation of Solution

Sodium Bicarbonate $\left({\text{NaHCO}}_3\right)$

It is commonly known as baking soda, having chemical formula $\left({\text{NaHCO}}_3\right)$. It is a salt composed of sodium cation $\left({\text{Na}}^{+}\right)$ and a bicarbonate anion $\left({\text{HCO}}_3{}^{-}\right)$. It appears as a white crystalline, odorless solid having pH nearly 8-8.5, which indicates that it is an alkaline salt and has a bitter taste.

It is widely used, not only in laboratories and industries, but also in households. A few of its applications are as:

It is used to extinguish small grease or electric fires by being thrown over the fire because sodium carbonate releases carbon dioxide when heated. The carbon dioxide does not react with burning materials and also does not conduct electricity. Therefore, it is the ideal gas to be used as an extinguisher.

It also helps treat acid indigestion and heartburn. The stomach contains acid $\left(\text{HCl}\right)$, which helps breakdown food but sometimes excess secretion of acid in the gastric glands causes an imbalance in the pH level of the stomach, and sodium bicarbonate is used as an antacid, which helps maintain the pH of the stomach by neutralizing the excess acid.

${\text{NaHCO}}_3\text{ + HCl }\to {\text{ NaCl + H}}_2{\text{O + CO}}_2$

It is primarily used in baking as a leavening agent. When it reacts with an acid, it releases carbon dioxide, which causes expansion and softens of batter. It provides a unique texture that is used for preparing cakes, pancakes, bread, and pizza base and so on.

It is used as a cleansing agent because it is a mild alkali and causes dirt and grease to dissolve in water, which is important for effective cleaning of the surface. It is mild, therefore, it is safe and effective to use as a glass cleaner, plastic cleaner and so on.

Calcium Carbonate $\left({\text{CaCO}}_3\right)$

Calcium carbonate is the principle component of limestone. It is also found in pearls, shells in the marine organisms, and is commonly used as chalk in classrooms.

It is a salt of the bivalent calcium cation $\left({\text{Ca}}^{2+}\right)$ and the bi-dentate carbonate anion $\left({\text{CO}}_3{}^{2-}\right)$. It is an odorless, fine crystalline powder and has a wide range of applications. Some of them are as:

It is a commonly used mineral in building materials and constructional applications. It not only improves performance but also provides cost benefits to a wide range of industrial environments. But due to weathering, it is now used as a raw material.

It also used in drugs as it acts an antacid to relieve heart burn, acid indigestion and an upset stomach. Also, it is used to treat or prevent low calcium levels in the people who do not get enough calcium from their diet.

It is used as a raw material for refining sugar from sugar beet. It is heated with anthracite to form calcium oxide and carbon dioxide. They both help precipitate out the impurities present in raw sugar.

It is also used in toothpaste as it represents a safe and a natural choice of providing abrasions in the toothpaste and helps remove plaque from teeth.

Ammonia

It is a compound of nitrogen and hydrogen having chemical formula $\left({\text{NH}}_3\right)$. It is a colorless gas, has a pungent odor and causes irritation to eyes, nose, throat, and skin. Aqueous form of ammonia is referred to as ammonium hydroxide. It is essential for various biological process and has a number of applications. Some of them are as:

It is used for cleaning purposes, generally the ammonia that is used in homes is in a diluted form (ammonium hydroxide). It is used for cleansing because it effectively breaks down household grime, stains, or oils from the surface and thus, it is easy to wipe out the stains.

It plays a major role in manufacturing fertilizers as it is the chief source of nitrogen which is essential for photosynthesis, growth of plants and other essential biological activities. It reacts with water to form aqua ammonia, a popular nitrogen fertilizer.

It is a versatile laundry additive, as it helps in removing and dissolving stains. When it reacts with water, it forms the ammonium ion $\left({\text{NH}}_4{}^{+}\right)$, and becomes a molecule having both, a hydrophobic part and a hydrophilic part. Grease is attracted to the hydrophobic part and tends to be drawn out from the cloth and the cloth is cleaned.

It is also used in manufacturing of explosives, especially ammonium nitrate, which is manufactured by reacting ammonium hydroxide with concentrated nitric acid. It is widely used as a component of explosive mixtures like ANFO (ammonium nitrate fuel oil).

${\text{HNO}}_{\text{3}}{\text{ + NH}}_3\to {\text{ NH}}_4{\text{NO}}_3$

Sodium Hydroxide (NaOH)

It is popularly known as caustic soda, having molecular formula $\left(\text{NaOH}\right)$. It is a white solid compound, which consists of sodium cations $\left({\text{Na}}^{+}\right)$ and hydroxide anions $\left({\text{OH}}^{-}\right)$. It is highly soluble in water and readily absorbs moisture from the air. Some industrial applications of sodium hydroxide are as:

It is used in treatment of water. This treatment is used when the pH of water is less than 7 and it becomes corrosive. Sodium hydroxide raises the pH of water to nearly 7 by neutralizing the excessive acid present in water.

It is used in manufacturing of soap. The solution of NaOH is treated with triglycerides from oil or fat, and it forms glycerol and sodium salt of fatty acids. This sodium salt of fatty acid is known as a soap.

It is also used in petroleum production and refining. It is used to remove impurities such as sulphur compounds and carbon dioxide, known as caustic washing. Removing these impurities is a necessary requirement to remove the corrosive elements and to give a usable product.

It is a used in printing, because of its capability of dissolving amphoteric metals and compounds. It reacts with aluminum in the presence of water, to form sodium aluminate and hydrogen gas. This sodium aluminate is also used in the paper industry, water softening and so on.

${\text{NaOH + Al + H}}_2\text{O }\to {\text{ NaAlO}}_2{\text{ + 3H}}_2$

Conclusion

Applications of bases are not limited to scientific laboratories. They have prominent uses in day-to-day activities. Apart from medicinal uses, they are used as cleansing products and in manufacturing of day-to-day items like soap, plastics and so on.