What Happens When Egg Shell is Added to Nitric Acid
When an egg shell is added to nitric acid, a chemical reaction takes place between the calcium carbonate present in the egg shell and nitric acid. During the reaction, calcium nitrate, carbon dioxide, and water are formed. The release of carbon dioxide can be observed as bubbles or effervescence around the egg shell.
This is a common example of the reaction between a carbonate and an acid and is useful for understanding the properties of acids, carbonates, and gas evolution reactions.
What Is Egg Shell Made Of?
The main inorganic component of an egg shell is calcium carbonate (CaCO₃). This compound gives the shell its hard structure.
When calcium carbonate comes into contact with an acid such as nitric acid (HNO₃), it reacts to produce a salt, water, and carbon dioxide gas. Therefore, the reaction of an egg shell with nitric acid can be understood as an acid-carbonate reaction.
What Happens When Egg Shell Is Added to Nitric Acid?
When pieces of egg shell are placed in nitric acid, the acid starts reacting with the calcium carbonate in the shell. One of the most noticeable observations is the formation of bubbles on the surface of the egg shell.
These bubbles are produced because carbon dioxide (CO₂) gas is released during the reaction. As the calcium carbonate continues reacting, the solid egg shell gradually dissolves.
The chemical reaction is:
CaCO₃ + 2HNO₃ → Ca(NO₃)₂ + CO₂ + H₂O
Here:
CaCO₃ = Calcium carbonate present in the egg shell
HNO₃ = Nitric acid
Ca(NO₃)₂ = Calcium nitrate
CO₂ = Carbon dioxide gas
H₂O = Water
Thus, the overall reaction can be represented as:
Egg shell + Nitric acid → Calcium nitrate + Carbon dioxide + Water
Why Does the Egg Shell Produce Bubbles?
The bubbling occurs because carbon dioxide gas is formed as a product of the reaction.
Carbonates generally react with acids to produce salt, water, and carbon dioxide. In this case, the carbonate component of calcium carbonate is converted into carbon dioxide and water, while calcium combines with nitrate ions to form calcium nitrate.
Therefore, the visible effervescence is evidence that a chemical reaction is taking place.
What Are the Observations in This Reaction?
When egg shell is added to nitric acid, students can identify several changes:
Bubbles or effervescence appear around the egg shell.
Carbon dioxide gas is released during the reaction.
The egg shell gradually dissolves as calcium carbonate reacts with the acid.
Calcium nitrate remains in the resulting solution, while carbon dioxide escapes as a gas.
Water is also formed as one of the products.
These observations help demonstrate the characteristic reaction of a carbonate with an acid.
How Can Carbon Dioxide Be Confirmed?
The carbon dioxide released during the reaction can be tested by passing the gas through limewater.
Carbon dioxide reacts with calcium hydroxide in limewater to form insoluble calcium carbonate, which makes the solution appear milky or cloudy. This is a commonly used test for carbon dioxide.
The reaction can be represented as:
CO₂ + Ca(OH)₂ → CaCO₃ + H₂O
The formation of calcium carbonate causes the characteristic milky appearance.
Why Does the Egg Shell Eventually Dissolve?
The egg shell contains calcium carbonate in a solid form. Nitric acid reacts with this calcium carbonate at the surface of the shell. As the reaction continues, more of the calcium carbonate is converted into soluble calcium nitrate, while carbon dioxide escapes from the mixture.
As a result, the solid material of the shell gradually decreases and can eventually dissolve when sufficient acid is available.
The speed of the reaction can depend on factors such as the amount and concentration of acid, the surface area of the egg shell, and the reaction conditions.
What Type of Chemical Reaction Is This?
The reaction between egg shell and nitric acid is an acid-carbonate reaction.
It can also be described as a reaction in which an acid reacts with a carbonate to produce:
Salt + Water + Carbon dioxide
The general form is:
Metal carbonate + Acid → Salt + Water + Carbon dioxide
For an egg shell:
Calcium carbonate + Nitric acid → Calcium nitrate + Water + Carbon dioxide
This reaction is therefore a useful example for students studying acids, bases, salts, and chemical reactions.
Why Is This Reaction Important in Chemistry?
This simple reaction demonstrates several important chemistry concepts at the same time. Students can understand how the composition of a substance determines its chemical behavior and how acids react with carbonates.
It also provides a straightforward example of gas evolution. The formation of bubbles makes the reaction easy to observe, while the limewater test provides a way to identify the carbon dioxide produced.
For 12th class chemistry question, this reaction can therefore help students connect a chemical equation with an observable laboratory change.
Role of pH in the Reaction
Nitric acid is a strong acid, so its presence makes the reaction mixture highly acidic. The pH (Potential of Hydrogen) of a solution is used to describe how acidic or basic it is, with lower pH values generally indicating greater acidity. Understanding pH can therefore help students connect this reaction with the broader concepts of acids, bases, and acid-base reactions.
Frequently Asked Questions
What happens when egg shell is added to nitric acid?
The calcium carbonate in the egg shell reacts with nitric acid to form calcium nitrate, carbon dioxide, and water. Carbon dioxide is released as bubbles, and the egg shell gradually dissolves.
What gas is released when egg shell reacts with nitric acid?
Carbon dioxide (CO₂) gas is released when calcium carbonate in the egg shell reacts with nitric acid.
What is the chemical equation for egg shell and nitric acid?
The balanced chemical equation is:
CaCO₃ + 2HNO₃ → Ca(NO₃)₂ + CO₂ + H₂O
Why does limewater turn milky?
The carbon dioxide produced in the reaction reacts with calcium hydroxide in limewater to form insoluble calcium carbonate. This makes the limewater appear milky.
What salt is formed when egg shell reacts with nitric acid?
The salt formed is calcium nitrate, Ca(NO₃)₂.
