Acids, Bases and Salts

Acids and Bases

According to the Arrhenius theory, an acid is a substance that increases the concentration of hydronium ions (H3O+) in a solution, and a base is a substance that increases the concentration of hydroxyl ions (OH-) in a solution. As per the Brønsted-Lowry theory, an acid is a substance that can act as a proton (H+) donor, and a base is any substance that acts as a proton acceptor. According to Lewis’s definition, an acid is a substance that can accept a pair of electrons, whereas a base is a substance that donates electron pairs.

Acids have a sour taste and turn blue litmus paper red, whereas bases are bitter and turn red litmus paper blue.

Chemical properties of Acids and Bases

You can determine the chemical properties of acids and bases by observing the colour shift of an indicator such as litmus or phenolphthalein.

Reaction with metals

When an acid reacts with metals, hydrogen gas is produced, and a salt is generated. The salt generally has the same name as that of the acid.

Acid + Metal → Salt + Hydrogen gas

• When a base reacts with metals, a salt is formed that contains a negative ion consisting of the metal and oxygen

• Hydrogen gas is also formed as a by-product of the reaction

• Acids undergo a reaction with metals carbonates and hydrogen carbonates to form salts, carbon dioxide and water

Metal carbonate/Metal hydrogen carbonate + Acid → Salt + Carbon dioxide + Water

The interaction between an acid and a base results in the formation of salt and water and is referred to as a neutralisation reaction.

Base + Acid → Salt + Water

Metallic oxides react with acids to form salt and water. Because this reaction is analogous to that of a base with an acid, metallic oxides are referred to as basic oxides.

Metal oxide + Acid → Salt + Water

• The interaction between a non-metallic oxide and a base is analogous to the reaction between a base and an acid since non-metallic oxides are naturally acidic

• Acidic and basic solutions in water conduct electricity due to the formation of hydrogen and hydroxide ions, respectively

• Alkalis are bases that are soluble in water

• The process by which an acid or a base dissolves in water is very exothermic

• When an acid or base is combined with water, the concentration of ions per unit volume decreases

• This is referred to as dilution, and the acid or base is said to have been diluted

Strength of Acid or Base Solutions

• The strength of acid or base solutions is proportional to the amount of H+ and OH– ions generated

• Strong Acids: Acids that produce a large amount of H+ ions.

• Weak acids: Acids that produce a small amount of H+ ions

• The strength of acid or base solutions may be determined using a scale known as the pH scale (range, 0-14), which indicates the concentration of hydrogen ions in a solution

• The p in pH stands for ‘potenz,’ which means ‘power’ in German

• The higher the concentration of hydronium ions, the lower the pH value

• A neutral solution has a pH value of precisely 7, an acidic solution has a value less than 7, and a basic solution has a value more than 7

Importance of pH in everyday life

Plants and animals’ pH sensitivity:

• Living creatures can only exist within a very restricted pH range

• The human body can function when the pH range is around 7.0 to 7.8

• Acid rain occurs when the pH of rainfall falls below 5.6

• When acid rain enters rivers, it degrades the water’s pH

• Aquatic life has a tough time surviving in such water bodies.

• Soil pH: Plants need a precise pH range to grow and thrive

Our digestive system’s pH value:

• Hydrochloric acid is produced in the stomach and aids in the digestion of meals

• Indigestion occurs when the stomach generates an abnormal amount of acid, resulting in discomfort and irritation

• People take antacids to alleviate this stomach ache caused by indigestion

• To neutralise the excess acid, antacids such as magnesium hydroxide (base) need to be consumed

pH as a factor in tooth decay:

• Tooth decay begins when the mouth’s pH falls below 5.5

• Toothpaste is usually basic and acts as a buffer against excess acid, preventing tooth decay

Examples of animal and plant self-defence via the generation of chemicals:

• The sting of a bee produces an acid that causes pain and discomfort

• Nettle leaves’ stinging hair inject methanoic acid, creating scorching agony

Applying a moderate base, such as baking soda, to the stinging region soothes it and provides comfort.

Conclusion

So, this was all about acids and bases. We hope this article will help you understand the concepts of acids and bases and how they undergo dissociation. The Arrhenius concept is a great way to understand acid-base equilibrium and how they affect the reaction as a whole.