What are acids and bases?

Acid

The basic definition of an acid is that it tastes or, when dissolved in water, changes the colour of blue litmus paper to red. When acid reacts with some metals, it produces H2 gas, and when a base reacts with an acid, it forms salt and water.

Some other technical definitions of acid are:

  • A substance that increases the concentration of hydronium ions in a solution is called acid.
  • In other words, a substance that can act as a proton donor is termed acid.
  • Also, a substance that can accept a pair of electrons is called acid.

The pH of acid varies Between zero to 7 depending on the acidic strength of the acid. 

Some common examples of acids are sulphuric acid (used in car batteries), tartaric acid (used in baking, and acetic acid (in vinegar).

Base

The basic definition is that it tastes bitter in an aqueous solution. It changes red litmus paper to blue, and the Base reacts with an acid to form salt and water.

Some other technical definitions of the base are:

  • A compound that donates a Hydroxide ion in a solution Is termed a base.
  • A substance that is capable of accepting a proton is called the base.
  • A compound capable of losing an electron pair is called the base.
  • The pH of the base varies between 7 to 14, depending on the basic strength of the base. 

Some common examples of the base are sodium hydroxide, NaOH, also known as lye or caustic soda (used in detergents and soaps), and Magnesium Hydroxide (commonly known as milk of magnesia).

Properties of acids and bases

Physical properties of acid

  • Acids in aqueous solution form electrolytes. These electrolytes produce hydroxide ions in water. Acids that produce a higher concentration of hydroxide ions are known as strong acids, and ones that produce fewer hydroxide ions are termed weak acids.
  • Acidic solutions or things that contain acid are sour.
  • When a chemical reaction between an acid and a base, they form neutral compounds salt and water.
  • Acids, when reacted with indicators, show confirmation results of their presence, like blue litmus paper turns red when tested with acid, and phenolphthalein turns colourless when treated with an acid.

Chemical properties of acids

  • Acids react with Reactive Metals.

The reaction between acids and metal is as follows

Acid + metal → salt + hydrogen         

Copper and silver do not react with dilute acids, for example,        

2HCl(aq) + Mg(s) → MgCl2(aq) + H2(g)  

Zn(s) + H2SO4 (aq) →ZnSO4 (aq) + H2(g)

  • Acids React with Bases        

 Acid + Base -> salt + water        

 6HNO3(aq) + Fe2O3(s) → 2Fe(NO3)3(aq) + 3H2O(l)     

 This is the reaction of acids and bases with metals.

  • Acids React with Carbonates 

Acid + carbonate => any salt + water + carbon dioxide

H2SO4(aq) + CuCO3(s) →CuSO4(aq) + H2O(l) + CO2(g)    

So these are the chemical properties of acids and bases.

  • Acids React with Bases    

Acid + Base -> salt + water  

6HNO3(aq) + Fe2O3(s) → 2Fe(NO3)3(aq) + 3H2O(l)    

This is the reaction of acids and bases with metals.

  • Acids React with Carbonates 

Acid + carbonate => any salt + water + carbon dioxide   

H2SO4(aq) + CuCO3(s) →CuSO4(aq) + H2O(l) + CO2(g)

Physical properties of the base

  • An aqueous solution of basis Are also electrolyte in nature but are quite weaker than that of aci.
  • Food containing bases are bitter. Also, the texture of bases is quite slippery, like soap.
  •  It also represents Its presence when treated with indicators. Red litmus paper turns blue when tested with base. Also, when phenolphthalein is treated with Base, it turns pink.
  •  The base does not react with metals, unlike acid.

React with acid to form water and salt.

Chemical properties of the base

  • Reactions of Bases with Metals

Alkalis (bases that are soluble in water) react with the metal to produce salt and hydrogen gas. For example, the reaction of zinc with sodium hydroxide.

NaOH (aq) + Zn(S) → Na2ZnO2 + H2(g)

  • The Reaction of Non-metal Oxide with Bases

Non-metal oxides react with bases to produce salt and water. For example, carbon dioxide and lime water (calcium hydroxide) reactions.

CO2 + Ca(OH)2 → CaCO3 + H2O

  • The Reaction between Acids and Bases

Acid + Base -> salt + water

6HNO3(aq) + Fe2O3(s) → 2Fe(NO3)3(aq) + 3H2O(l)

It is the reaction of acids and bases with metals.

  • Reactions between bases and water

The following reaction represents the general reaction between a base (B) and water to produce a conjugate acid (BH+) and a conjugate base (OH−):

B(aq) + H2O(l) ⇌ BH+(aq) + OH-(aq)

The equilibrium constant, Kb, for this reaction can be found using the following general equation.

Kb = [BH+][OH-]/B

Conclusion

Generally, a proton donor is called Acid, whereas the one which accepts that donated proton is called the base. The above article explains the concept of acid and base in a much wider concept. Read the above article carefully to understand the concept of acid and base. Hope this article helped you.