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# Importance of pH in Everyday Life

Acids, bases, and salts have an impact on chemistry as well as our daily lives. Acids have a sour flavour (the word acid comes from the Latin word ‘acere’ which means ‘sour’), bases have a bitter taste, while salts themselves have a salty taste. Citric acid is found in fruits such as oranges and lemons, tartaric acid in tamarind, malic acid in apples, and lactic acid in milk and milk products, as well as hydrochloric acid in gastric fluids. Many bases, such as lime water, can also be found.

Many of these acids are used in our daily lives, such as vinegar or acetic acid in the kitchen, boric acid in laundry, baking soda in cooking, washing soda in cleaning, and so on. Many acids and bases that we do not use in our daily lives are utilised in laboratories and industries, such as HCl, H2SO4, and NaOH, KOH, among others. The neutralisation process results in the creation of salt and water when these acids and bases are mixed in the proper quantities. NaCl and KCl, for example, are naturally occurring salts found in seawater and natural rock deposits.

### What is pH?

pH stands for Potential of Hydrogen and is defined as the logarithm of H+ ion concentration. The pH value of any substance or solution indicates whether it is acidic, neutral, or alkaline.

The term pH was first introduced by Soren Peter (Biochemist), in 1909. To determine the strength of acids and bases, we use a universal indicator that shows different colours at different concentrations of hydrogen ions in a solution. The value of pH is generally used to quantitatively determine the strength of acid and base.

The equation used for calculating the pH:

pH = -log [H+]

### pH Chemistry

A pH scale is a tool for determining the concentrations of acids and bases. The scale runs from 0 to 14, with 0 being the lowest and 14 being the highest. Litmus paper is a test that determines if a substance is acidic or basic. The paper’s colour corresponds to the numbers on the pH scale, indicating the type of chemical being tested. Vinegar, for example, is an acid with a pH of 2.4 on the pH scale.

Doctors and scientists generally agree that maintaining a good pH balance is important for overall health. The food and drink you ingest determine the pH level, or possible level of hydrogen, in your body. The concentration of hydrogen ions determines the pH. On a scale of 0 to 14, this computation is made.

The pH scale is logarithmic, indicating the concentration of hydrogen ions in a solution in inverse order. Because the pH formula approximates the molar concentration of hydrogen ions in a solution to the negative of the base 10 logarithms, this is the case. pH is defined as the negative of the H+ ion’s activity expressed in base 10 logarithms. The pH scale can be traced back to a set of standard solutions whose pH has been agreed upon internationally. Primary pH standard values are derived using a concentration cell with transference by calculating the potential difference between a hydrogen electrode and a standard electrode such as the silver chloride electrode. The pH of aqueous solutions can be measured with a glass electrode and a pH metre, or a colour-changing indicator.

### What is pH value?

To find the pH value of a component we use a pH scale. The pH scale has values from 0 to 14, where 0 indicates very acidic, and 14 indicates very alkaline. 7 is the centre of the scale if any solution has a pH value of 7, it means that the solution is neutral in nature. The values less than 7 indicated that the solution is acidic and values more than 7 indicate that the solution is alkaline.

pH scale

As we go from 7 to 1 the acidity of the solution increases i.e a solution with pH value of 2 is more acidic than a solution with pH value of 3. The alkalinity of a solution increases from 7 to 14 (opposite to the acidity)  i.e a solution with pH value of 11 is more alkaline than a solution with pH value of 9.

### pH Indicator

An indicator that determines whether a solution is acid or basic is known as a pH indicator. Generally, the indicator causes the colour of the solution or paper to change depending on the pH value. There are different types of indicators some are solid and some are liquid in nature. But, the most common indicators are found in the form of strips of paper, known as the Litmus paper. It changes its colour to red when added to an acidic solution and gives a blue colour when tested with a basic solution.  Also, there are various other ways to make indicators at home.

Chemicals from the naturally coloured anthocyanin family are found in many plants and plant components. In acidic solutions, they are red, and in basic solutions, they are blue. Anthocyanins can be extracted from a variety of coloured plant parts using water or other solvents, such as leaves (red cabbage), flowers (geranium, poppy, or rose petals), berries (blueberries, blackcurrant), and stems (rhubarb). A typical beginning chemistry demonstration is extracting anthocyanins from common household plants, particularly red cabbage, to make a primitive pH indicator.

### Limitations of pH Scale

1. The pH of a 1N strong acid solution is zero.
2. pH is negative for concentrations 2N, 3N, ION of strong acids.
3. At greater concentrations, Hammett acidity functions are employed instead of pH.

### Importance Of pH in Everyday Life

Digestive System

In the human body, all the physiological reactions take place at the pH of 7 – 7.8. Hydrochloric acid is secreted as food enters the stomach(turns the pH of the stomach between 1 and 3) because of overeating or various reasons excess of HCl (hydrochloric acid) is released. The excess of HCl in the stomach causes indigestion which produces pain and irritation (pH level of the stomach decreases). To cure indigestion, we can take bases called antacids (anti-acid). Antacids are a group of mild bases. Being basic in nature, they react with excess acid in the stomach and neutralise it. (which have no toxic effects on our body)

Common antacids used for curing indigestion due to acidity are:-

• Milk of Magnesia (Magnesium hydroxide)

Mg(OH)2(s) + 2HCl(aq) → 2H2O(l) + MgCl2(aq)

• Baking Soda (Sodium hydrogen carbonate)

NaHCO₃ + HCl ➝ NaCl + CO₂ + H₂O

Tooth Decay

When we eat food, the bacteria present in our mouths break down the sugar to form acids. The acid lowers the pH in the mouth making it acidic. When the pH of the mouth falls below 5.5, our tooth starts decaying. Tooth Decay happens because the acid becomes strong enough to attack the enamel (of our teeth) and corrode it. The best way to prevent tooth decay is to clean the mouth thoroughly after eating food. Many kinds of toothpaste contain bases to neutralise mouth acid (The pH of toothpaste being about 8.0). So using toothpaste for cleaning the teeth can neutralise the excess acid in the mouth.

Plants and Animals are Sensitive to pH changes

Most of the plants grow best when the pH of the soil is close to 7. If the soil is too acidic (low pH), then it is treated with:-

• Quicklime (Calcium Oxide)
• Slaked lime (Calcium Hydroxide)
• Chalk (Calcium Carbonate).

If the soil is too alkaline then it can be reduced by adding Manure or Compost (decaying organic matter) which contains acidic materials. The pH also plays an important role in the survival of animals, including human beings. The aquatic animals can survive in water bodies within a narrow range of pH change. The high acidity of water bodies can kill aquatic animals. Calcium Carbonate is often added to acidic lake water to neutralise the acid that comes from acid rain.

Self Defence by Animals and Plants through Chemical Warfare

When a honey bee stings a person, it injects Formic Acid into the skin. By rubbing a mild baking soda neutralises the acidic liquid injected by a bee sting. When a wasp stings, it injects an alkaline liquid (Methanoic Acid(HCOOH)) into the skin causing burning pain. By rubbing mild acid vinegar on the stung area gives relief. When a person touches the leaves of a nettle plant, the stinging hair of nettle leaves injects Methanoic Acid into the skin. It can be neutralized by rubbing Baking Soda or Dock Plant which grows beside the nettle plant and is basic in nature.

HCOOH + NaHCO3 ⟶ HCOONa + CO2 + H2O

Lemon juice to clean copper vessels

A dull green coloured film forms on a copper vessel when it is exposed to damp air over an extended period of time. Copper hydroxide (Cu(OH)2) and copper carbonate (CuCO3) are combined to form this greenish layer.

The reaction is,

2Cu + H2O + CO2 + O2 ⟶ Cu(OH)2 + CuCO3

Because these goods are basic in nature, acidic substances such as lemon or tamarind juice are required to clean them. These sour compounds are chosen for cleaning since they are good at cleaning copper vessels.

### Sample Problems

Question 1: What does the pH value of any solution indicate?

The pH value of any solution indicates whether it is acidic, neutral, or basic. Also, it is used to determine the strength of acid and base.( As we go from 7 to 1 the acidity of the solution increases i.e a solution with pH value of 2 is more acidic than a solution with pH value of 3. The alkalinity of a solution increases from 7 to 14 (opposite to the acidity)  i.e a solution with pH value of 11 is more alkaline than a solution with pH value of 9.)

Question 2: Group the following solutions according to their nature (acidic, basic or neutral) and arrange them in order of their concentration and state which is more acidic and basic (pH values of the solution are given in the bracket):-

Solution 1(8), Solution 2(3), Solution 3(10), Solution 4(7),  Solution 5(13), Solution 6(1)

• Acidic – Solution 6(1), Solution 2(3)

Solution 6 is the most acidic solution as it has the least pH value.

• Basic – Solution 5(13), Solution 3(10), Solution 1(8)

Solution 5 is the most basic solution as it has the highest pH value.

• Neutral – Solution 4(7)

Question 3: What is the normal pH level inside a Human stomach? Why does the pH level decrease while digestion?

In the human body, all the physiological reactions take place at the pH of 7 – 7.8. A decrease in the pH level is observed while digestion because HCl is released inside the stomach to break down the food into simple compounds so it can be absorbed by the body.

Question 4: Name the common antacids used for curing indigestion due to acidity.

Common antacids used for curing indigestion due to acidity are:-

• Milk of Magnesia (Magnesium hydroxide)

Mg(OH)2 (s) + 2HCl (aq) → 2H2O (l) + MgCl2 (aq)

• Baking Soda (Sodium hydrogen carbonate)

NaHCO₃ + HCl ➝ NaCl + CO₂ + H₂O

Question 5: How can you neutralise the effect of Bee stings on a human body?

When a honey bee stings a person, it injects Formic Acid into the skin. By rubbing a mild baking soda neutralises the acidic liquid injected by a bee sting.

HCOOH + NaHCO3 ⟶ HCOONa + CO2 + H2O

Question 6: What can be added to soil to reduce its acidity and make it suitable for crops to grow?

Following substances can be added to the soil to neutralise its acidity:-

• Quicklime (Calcium Oxide)
• Slaked lime (Calcium Hydroxide)
• Chalk (Calcium Carbonate)

Question 7: You are been provided with three test tubes. One of them contains distilled water and the other two contain an acidic solution and a basic solution, respectively. If you are given only red litmus paper, how will you identify the contents of each tube?