Reactions and Commonalities

Key Concepts

• Reaction of bases with metal bicarbonates
• Neutralization reaction
• Combination of a neutralization reaction
• Strengths of acids and bases
• Differences between acid and base

Introduction:

Acid and base are the forms of chemicals that play a crucial role in chemistry. Acids are substances that are bitter in taste and bases are substances that are sour in taste. Acids can react with many substances like metals, metal carbonates, oxides to give corresponding salts and water. Bases react with metals but not with metal carbonates or metal bicarbonates to give products, because metal carbonates themselves act as a base. 

When acid and base react with water it produces H⁺ions and OH^– ions, respectively. Non-metal oxides are acidic in nature. For example, carbon dioxide is a non-metal oxide. When carbon dioxide is dissolved in water it produces carbonic acid. 

Acids and bases are very important in our day to day life. Some of the significance of acids are; hydrochloric acid released in our stomach aids in the digestion of food, pH of the rain is less than 5.6 then we call it as acid rain, flowing of acid rain in water bodies makes the threat to the survival of aquatic life. 

Explanation: 

Now let’s learn the chemical properties of acids and bases. 

Chemical properties of Acids and Bases 

1. Reaction of acids with bicarbonates: 

Acids react with metal bicarbonates to give the respective salts and water in addition to carbon dioxide. The mixture forms foam as carbon dioxide is produced and it gets expanded. 

Examples: Sodium bicarbonate reacts with acetic acid to give sodium acetate, water and CO₂ 

Calcium carbonate is reacting with sulphuric acid to give calcium sulphate, water and carbon dioxide. 

The gas evolved in this reaction is carbon dioxide in the form of effervescence. 

Test for the evolution of CO₂ 

Take two test tubes and label them as A and B. Take 0.5gm of sodium carbonate(Na₂CO₃) in test tube-A and take the same amount of sodium bicarbonate(Na₂HCO₃) in test tube B. Add 2mL of dil.HCl in both the solutions. We observe the gas is produced in both the test tubes. Pass the gas produced in each test tube through lime water. Carbon dioxide  evolves due to the reaction of an acid with Na₂CO₃ and Na₂HCO_3,in the form of brisk effervescences. 

The reactions happening in the above activity is as follows: 

Sodium bicarbonate reacts with dilute hydrochloric acid to give salt, carbon dioxide and water. 

When passed through lime water, carbon dioxide turns it milky white. This is used as a test to check the presence of CO₂. 

When CO₂ is passed in excess, then the milkiness of the substance disappears. 

Limestone, chalk and marble are the different forms of calcium carbonates, and when acids react with metal carbonates or metal bicarbonates it gives salts, CO₂ and water. 

Bases do not react with metal carbonates and metal bicarbonates and they do not give any reaction. 

Metal carbonates and metal bicarbonates themselves act as a base. 

Alkali 

All bases do not dissolve in water but whereas alkali is a base that dissolves in water. Some of the common alkalis are Calcium hydroxide, Sodium or potassium hydroxide etc. 

All alkali are bases but all bases are not alkali 

2. Reaction between acids and bases: 

Neutralization reaction: 

A neutralization reaction is one of the types of double displacement where elements get displaced with each other and form a compound. 

In double displacement upon reaction, we get salt and water. 

Acid gets decomposed to give H⁺ ion and anion. Bases get decomposed to give OH^– ions and cation. Both these combine together and give salt and water. 

In a neutralization reaction, the H⁺ of acid gets neutralized by one OH^– ion of bases and form a water molecule. The H⁺ion taken from the acidic solution gets neutralized with the same number of OH^– from the basic solution combinedly called a complete neutralization reaction. 

The total amount of acid and base depends upon the total amount of H⁺ and OH^– produced by acids and base. 

The reaction between an acid and a base to give salt and water is known as a neutralization reaction. 

Combination of reactions that are of neutralization reactions: 

For the above combination of reactions, let’s see one by one how does it happens: 

1. Hydrochloric acid (Strong acid) reacts with Ammonia (Weak base) to give Ammonical chloride (Acidic Salt) and water.  

Strong acid + Weak base ®  Acidic salt + H₂O 

HCl + NH₃  ®  NH₄Cl + H₂O 

2. Acetic acid (Weak acid) reacts with Sodium hydroxide (Strong base) to give Sodium acetate (Basic salt) and water.  

Weak base + Strong acid ® Basic salt  + H₂O 

CH₃COOH + NaOH  ® CH₃COONa + H₂O 

3. Hydrochloric acid (Strong acid) reacts with Sodium hydroxide (Strong base) to give Sodium chloride (Neutral salt) and water. 

Strong acid + Strong base ® Neutral Salt  + H₂O 

HCl + NaOH ® NaCl + H₂O 

4. Acetic acid (Weak acid) reacts with Ammonia (Weak base) to give ammonia acetate and water. 

Weak acid + Weak base ® Neutral Salt + H₂O 

CH₃COOH + NH₃  ®  CH₃COONH₄ + H₂O 

Strength of acids and bases: 

• Acids in which the complete dissociation of hydrogen ion takes place is called a strong acid. Bases I which the complete dissociation of hydroxide ion takes place is called a strong base. 
• Strength of acids and bases depends on the number of H⁺ ions and OH^– ions. 
• By using universal indicators, we can find the strength of the acids and base as it shows different colors at different concentrations. 
• The scale for measuring the hydrogen ion concentration in a solution is called as P^H Scale. 

Variation in pH scale: 

Commonalities of acids and bases 

• All acids and some of the alkalis show corrosion action on skin as they form painful blisters when they contact the skin.  
• Most of the strong acids and bases shows corrosion and form rust. 
• Both the acids and bases are electrolytes which means that they are good conductors of electricity. 
• The reaction of acid and base is an exothermic reaction in which it releases heat. 

Differences of acids and bases: 

Summary

• Acids in reaction with metal bicarbonates give respective salts and water in addition to carbon dioxide. Carbon dioxide is a gas, the mixture will form foam as carbon dioxide is produced and it gets expanded.
• A neutralization reaction is one of the types of double displacement where elements get displaced with each other and form a compound.
• All bases do not dissolve in water but whereas alkali is a base that dissolves in water.
• Acid gets decomposed to give H+ ion and anion. Bases get decomposed to give OH-ions and cation. Both these combine together and give salt and water.
• Strength of acids and bases depends on the number of H+ ions and OH- ions.
• All acids and some of the alkalis show corrosion action on skin as they form painful blisters when they contact the skin.
• By using universal indicators, we can find the strength of the acids and base as it shows different colors at different concentrations.