Chemistry In Everyday Life

Bases convert red litmus into blue whereas acids convert blue litmus into red. This means aqueous solution of base will also convert red litmus into blue.

Solution of acids and bases are electrically good conductor. They contain a large number of ions.

i. When acid is dissolved in water, it releases hydrogen (H⁺) ions.

ii. When base is dissolved in water, it releases OH^- ions.

Both the ions (H⁺ and OH^-) act as charge carriers and hence conduct electricity.

pH is negative logarithm of hydrogen ion concentration present in any solution:

pH = -log[H⁺]

Note: pH scale was given by Sorenson in 1909. pH scale represents hydrogen ion concentration of any solution.

pH of any acidic solution is less than 7

pH of any basic/alkaline solution is greater than 7.

pH of any neutral solution is equal to 7.

Hence, among the given options, pH of any acidic solution is 4.

On the other hand, 7 shows the pH of any neutral solution.

11 and 14 show the pH of any basic solutions.

The digestion of food in our stomach occurs in acidic medium. Before food arrives in the stomach, the stomach normally has a pH between 5 to 6. As the food arrives and digestion takes place, the pH falls to 3 (acidic medium).

Sodium hydrogen carbonate (NaHCO₃) which is also known as baking soda or eatable soda.

i. Soda acid fire extinguishers contain a mixture of sulphuric acid and baking soda inside it.

ii. When knob of the fire extinguisher is pressed, sulphuric acid get mixed with baking soda which produces a lot of CO₂ gas.

iii. CO₂ gas covers the surroundings of fire.

iv. It stops the supply of air to the burning substance.

v. Hence, fire gets extinguished.

The chemical name of washing soda is sodium carbonate decahydrate. It contains ten water molecules of crystallization. The chemical formula of washing soda is Na₂CO₃.10H₂O.

When bleaching powder is kept open in air, it reacts with CO₂ which is present in air to form calcium carbonate and chlorine gas. The reaction takes place:

Thus, chlorine gas is released when bleaching powder is kept in open air.

Soaps work well in soft water. In hard water, soaps are not able to perform cleansing action. In hard water, calcium and magnesium salts of higher fatty acids are formed which are insoluble in water. They get precipitated. Hence, soaps work well in only soft water not in hard water.

In micelle formation:

i. Hydrophobic tail remains inside the solution and attracts the oily dirt.

ii. The hydrophilic polar head remains outside and reacts with water.

iii. Thus, oily dirt gets surrounded by a micelle.

According to Bronsted Lowry concept, bases are the substances which accept proton.

For example:

Here ammonia (NH₃) is a proton acceptor, hence it is base. Base

changes into conjugate acid (NH₄⁺) by accepting proton (H⁺)

The acid which is found in the sting of red ant is formic acid. This acid causes irritation and pain on skin. Not only red ant, but the sting of honeybees and spiders also inject formic acid into the skin.

According to Bronsted Lowry concept, acids are the

substances which donate proton.

For example:

Here water (H₂O) is a proton donor, hence it is acid. Acid

changes into conjugate base (OH^-) by losing proton (H⁺)

The reaction between an acid and a base to give a salt and water is called neutralization reaction. All acids get neutralized and loose their acidic properties when reacted with bases

Base + Acid → Salt + Water

For example: When sodium hydroxide (a base) and HCl (an acid) reacts together, they form a common salt (NaCl) and water:

NaOH + HCl → NaCl + H₂O

Drinking water can be disinfected by using bleaching powder [Ca(OCl)₂].

i. Bleaching powder is an agent which removes and kills the unwanted bacteria, microorganisms and germs in the drinking water.

ii. If the microorganisms and germs are not removed from drinking water, then it can cause number of harmful diseases.

iii. Hence, drinking water must be made disinfected by using bleaching powder.

When acid reacts with metallic oxide, it produces salt and water.

Metallic oxide + acid → Salt + water

For example: When copper oxide (metal oxide) reacts with hydrochloric acid, it forms copper chloride (salt) and water. The reaction takes place is given below:

CuO + HCl → CuCl₂ + H₂O

Metal oxides produce salt and water on reaction with acids, hence these are basic in nature.

In pH, “p” denotes a german term- potenz which means strength and “H” represents hydrogen. The pH scale was given by Sorenson in 1909.

We will use antacids like milk of magnesia [Mg(OH)₂] or Al(OH)₃ solution to treat acidity problem in the stomach.

These are the mild bases which neutralize the effect of hydrochloric acid produced in the stomach. These maintain the pH of stomach and as a result decrease acidity.

Two salts of sodium are:

Sodium chloride (NaCl)

When NaOH (base) and HCl (acid) are reacted togerther, give sodium chloride (common salt) and water.

NaOH + HCl → NaCl + H₂O

Sodium sulphate (Na₂SO₄)

When NaOH (base) and H₂SO₄ (acid) reacts together, they give sodium sulphate (salt) and water.

2NaOH + H₂SO₄→ Na₂SO₄ + 2H₂O

According to Lewis theory, bases are defined as “the substances which loose/donate electron pairs are called bases”. That is electrons pair species are bases.

For example:

In the above reaction, base donates a proton to acid (BH₃) which gives a Lewis complex.

When fatty acids like oil are heated with aqueous solution of sodium hydroxide or potassium hydroxide, form soaps which are the sodium or potassium salts of fatty acid containing long hydrocarbon chain from C₁₂ to C₁₈. This process is called saponification reaction.

In the above reaction, soaps get separated by adding sodium chloride.

Properties of detergents are:

i. Detergents work well both in soft water as well as hard water.

ii. These are sodium alkyl sulphonates.

iii. When detergents perform cleansing action, scum is not formed.

Plaster of Paris (CaSO₄.1/2 H₂O) is used to join fractured bones. When Plaster of Paris is mixed with water and applied around the fractured bones, it becomes solid and sets into a hard mass. Hence, it is used to join the fractured bones.

Given:

Concentration of hydrogen ion = [H⁺] = 1 × 10^-4

To calculate the pH of this solution, apply the formula given below:

pH= -log [1 × 10^-4]

pH= -log [ -4 log 10]

pH= log 4

pH = 0.602

pH of the solution is 0.6. Hence it is an acidic solution (less than 7)

Difference between soap and detergents:

According to Arrhenius theory:

Acids are the substances which release hydrogen ion when dissolved in water.

For example: HCl → H⁺ + Cl^-

HNO₃→ H⁺ + NO₃^-

These both are acids (hydrochloric acid and nitric acid) because they release H⁺ ion in the aqueous solution.

The acids which are completely ionized in the solution are called strong acids. But some acids are incompletely ionized in water, are called weak acids.

Bases are the substances which release hydroxyl ions (OH^-) when dissolved in water.

For example NaOH → K⁺ + OH^-

KOH → K⁺ + OH^-

These both are bases (sodium hydroxide and potassium hydroxide) because they release OH^- ion in the aqueous solution.

The bases which are completely ionized in the solution are called strong bases. But some bases are incompletely ionized in water, are called weak bases.

pH scale:

i. It is used to measure the strength of any acid or base.

ii. It represents hydrogen ion concentration ([H⁺]) of any solution.

iii. “p” stands for potenz which means strength and “H” stands for hydrogen.

iv. pH is a negative log of the concentration of hydrogen ions:

pH = -log [H⁺]

v. Acidic solutions have a pH less than 7.

vi. Basic solutions have a pH greater than 7.

vii. Neutral solutions have pH equal to 7.

viii. The strength of an acid depends upon the H⁺ and OH^- ions. Greater concentration of H⁺ ions shows strong acids and greater concentration of OH^- ions shows strong bases.

Water molecules of crystallization:

i. Salts mainly exist in crystalline form.

ii. Sometimes they have some water molecules present as crystallization water molecules.

iii. When we write chemical formula of salt along with a number of water molecules present, is called crystallization water molecules.

For examples:

Washing soda – Na₂CO₃.10H₂0

Here 10 molecules of water are present as water molecules of crystallization.

Gypsum – CaSO₄.2H₂O

Here 2 molecules of water are present as water molecules of crystallization.

When curd or sour substances are kept in metal utensils, they become toxic. Curd and sour substances are acidic in nature and when they kept in metal utensils, curd or sour substances react with them. This makes them toxic and can cause food poisoning to us. Hence, it is not advised to keep curd and sour substances in the metal utensils.

When teeth are not cleaned after food at night, some bacteria present in our mouth reacts with remains of food on teeth and produce acid. As a result, acid reduces the pH of mouth. If the pH falls to 5.5, then enamel of teeth can degrade.

Hence, it is advised by our elders that after food, cleaning of teeth is a must.

It is given that a compound A reacts with H₂SO₄ acid and releases gas B with effervescence. Gas B burns with a pop sound.

If the gas burns with a pop sound, this means gas B is hydrogen. Hydrogen gas gives pop sound when it burns.

The compound A must be a metal, i.e., zinc. When zinc reacts with H₂SO₄, it releases hydrogen gas and forms a salt. The reaction is:

Zn + H₂SO₄→ ZnSO₄ + H₂

Thus, compound A is zinc

B is hydrogen gas.

According to Bronsted Lowry theory:

Acids are the substances which donate a proton.

Bases are the substances which accept a proton.

They give conjugate acid-base pair concept.

For example:

Here water (H₂O) is a proton donor, hence it is acid. Acid

changes into the conjugate base by losing a proton (H⁺)

Ammonia (NH₃) is a proton acceptor, hence it is base. Base

changes into conjugate acid by accepting a proton (H⁺)

Uses of pH in daily life:

The stingof insects: When a honeybee, ant or spiders sting a person, they inject an acidic liquid (formic acid) into the body. This causes too much pain and irritation. Baking soda (sodium hydrogen carbonate NaHCO₃) is a mild non-corrosive base.

When it is applied to the stung area, it reduces the effect of acid by neutralizing the excess acid. As a result, the pain and irritation are reduced.

Acidity in the stomach: Acidity causes pain and irritation in the stomach. Milk of magnesia [Mg(OH)₂] or Al(OH)₃ solution are used to treat acidity problem in the stomach.

These are the mild bases which neutralize the effect of hydrochloric acid produced in the stomach. These maintain the pH of the stomach and as a result decrease acidity.

Tooth decay: When teeth are not cleaned after food at night, some bacteria present in our mouth reacts with remains of food on teeth and produce acid. As a result, acid reduces the pH of mouth. If the pH falls to 5.5, then enamel of teeth can degrade.

Hence, we should brush our teeth with toothpaste (basic) which reduces the effect of acid in the mouth.

(i) NaOH

Name: Sodium hydroxide

Methods of preparation: When a concentrated solution of sodium chloride is electrolyzed, it forms sodium hydroxide (NaOH), chlorine gas and hydrogen gas.

Chlorine gas is formed at the anode (positive charge) and hydrogen gas at the cathode (negative charge)

The reaction takes place is given as:

2NaCl + 2H₂O → 2NaOH + Cl₂ + H₂

The above reaction is called chlor-alkali process.

Uses:

a. It is used in the synthesis of soap, paper, and other chemicals.

b. It is used in the preparation of oils.

c. It is used in the refining of petroleum

Name: Sodium hydrogen carbonate or baking soda

Methods of preparation: Baking soda is prepared by passing carbon dioxide gas in the solution of sodium carbonate.

Uses:

a. It is used in fire extinguishers.

b. It is used as a mild antiseptic.

c. It is used as a laboratory reagent.

d. It is also used as an antacid to reduce acidity in the stomach.

Name: Sodium carbonate decahydrate or Washing soda

Methods of preparation: Washing soda is prepared by Solvay process. On heating baking soda, sodium carbonate is obtained

On recrystallization od sodium carbonate, washing soda is formed:

Na₂CO₃ +10H₂O + crystallization → Na₂CO₃.10H₂O

Uses:

a. It is used for washing and cleaning purpose.

b. It is used in paper, paint and textile industry.

c. It is used as a laboratory reagent.

Name: Bleaching powder or calcium hypochlorite

Methods of preparation:

When dry slaked lime is passed through chlorine gas, it forms bleaching powder. The reaction takes place is given as:

Uses:

a. It is used for disinfecting drinking water to make it germfree.

b. It is used for bleaching cotton and linen in the textile industry.

c. It is used to bleach dirty clothes in the laundry.

Name: Calcium sulphate hemihydrate or Plaster of Paris (POP)

Methods of preparation: When gypsum is heated upto 393K to produce Plaster of Paris.

Uses:

a. It is used in building construction.

b. It is mainly used to join fractured bones.

c. It is used in the formation of statues.

i. Soaps and detergents clean clothes in micelle formation.

ii. Soap contains a hydrophilic polar head and a hydrophobic tail.

iii. Soap molecules after ionization in water, arrange themselves around oily dirt in such a manner that generally spherically shaped micelles are formed.

iv. During micelle formation, hydrophobic tail attracts the dirt particles and remains inside whereas the hydrophilic polar head remains outside and reacts with water.

v. Thus, oil dirt gets surrounded by micelle.

vi. All micelles are negative charges. Hence, do not precipitate.

vii. As a result, when soaps are applied n dirty clothes in water, all dirt gets removed by water and clothes become clean.