Tag: Conservation of Mass

Introduction

Old chemical bonds are cleaved in a chemical reaction and form new bonds. Any chemical equation should be balanced properly. It means the number of each atom should be the same on both the reactant and product sides. It is based on two rules; the ‘law of conservation of masses’ and the ‘law of constant proportions’. If a reaction is considered to be \(X + Y{\rm{ }} \to {\rm{ }}Z + P\), then X, Y are called reactants, and Z, P are called products of this reaction.

Define the law of conservation of mass.

It is stated in this law: “The mass in an isolated system can neither be created nor be destroyed but can be transformed from one form to another”. So the number of each type of atom in a chemical equation is always the same on both sides of the equation.
Read More: Law of Conservation of Mass with Experimental

Define the law of constant proportions.

The law states that- “In a chemical substance, the elements are always present in definite proportions by mass”. In the \({H_2}O\) molecule, the molar mass of two H atoms is 2 gm/mole and the molar mass of one O atom is 16 gm/mole. So their ratio of mass is 2:16=1:8. This ratio in \({H_2}O\) is always constant.

What is a balanced chemical equation?

According to the two laws of conservation of mass and conservation of definite proportions, a chemical equation must be properly balanced. It means that the number of all the atoms or molecules involved in a chemical reaction must be the same on both the reactant and product side. This is known as a balanced chemical equation. 

Importance of coefficients and subscripts in balancing a chemical equation

Coefficients are numbers that help us to determine the number of each atom present in a balanced chemical equation. It can be changed necessarily.

Subscripts are the numbers that help to determine the chemical formula of any compound. The subscripts are always constant throughout a chemical equation.

\[{N_2} + {\rm{ }}3{\rm{ }}{H_2} \to {\rm{ }}2{\rm{ }}N{H_3}\]

Method of generating a balanced chemical equation- 

Suppose we are trying to balance this unbalanced chemical equation. 

\[C{H_4} + {O_2} \to {\rm{ }}C{O_2} + {H_2}O\]

These are the steps that are followed to make a balanced chemical equation. 

• At first, the number of each atom on both sides is determined.

Atoms present	Number of atoms on the reactants side	Number of atoms on the products side
C	1	1
O	2	3
H	4	2

• Then coefficients of each atom are balanced properly. For this equation, at first, the coefficients of H are balanced. So now the chemical equation transforms into- 

\[C{H_4} + {O_2} \to {\rm{ }}C{O_2} + 2{\rm{ }}{H_2}O\]

• Now the coefficient of O is balanced accordingly. So the new chemical equation is:

\[C{H_4} + 2{O_2} \to {\rm{ }}C{O_2} + 2{H_2}O\]

This is the balanced chemical equation: \(C{H_4} + 2{O_2} \to {\rm{ }}C{O_2} + 2{H_2}O\)

Balancing the chemical equation- 

\[{C_3}{H_8} + {O_2} \to {\rm{ }}C{O_2} + {H_2}O\]

• At first, the number of each atom on both sides is determined.

Atoms present	Number of atoms on the reactants side	Number of atoms on the products side
C	3	1
O	2	3
H	8	2

• Now the coefficient of C is balanced on both sides. So the chemical equation changes to-

\[{C_3}{H_8} + {O_2} \to {\rm{ }}3C{O_2} + {H_2}O\]

After equating the coefficients of H, the new equation is:

\[{C_3}{H_8} + {O_2} \to {\rm{ }}3C{O_2} + 4{H_2}O\]

• Then the coefficients of O are balanced accordingly to form a balanced chemical equation.

\[{C_3}{H_8} + 5{O_2} \to {\rm{ }}3C{O_2} + 4{H_2}O\]

This is the balanced chemical equation: \({C_3}{H_8} + 5{O_2} \to {\rm{ }}3C{O_2} + 4{H_2}O\)

In this way, any chemical equation can be balanced.

Summary

According to the laws of conservation of mass and conservation of constant proportions, any chemical equation should be balanced properly. This is done by equating the coefficients of each atom involved in a chemical reaction. Balancing a chemical equation is extremely important in the field of chemistry. Based on the coefficients present before the molecules involved in a chemical equation, the yield of the products of that reaction can be determined.                                         

Frequently Asked Questions

1. State the limitations of using chemical equations.

Ans: By any chemical equation we can’t understand the states(solid/liquid/gas) of the compounds involved. Again, the reversibility or irreversibility of any reaction can’t be determined by the chemical equation. 

2. What are the different types of chemical equations?

Ans: Depending on the nature of reactants and products in a reaction, it may be classified into five types. They are combination reaction, single replacement reaction, decomposition reaction, combustion reaction, and double replacement reaction. Some reactions fall under two categories simultaneously. 

3. What is the main reason behind a chemical reaction?

Ans: A chemical reaction can be described as a bond-breaking and bond-making process. It means all the old bonds are cleaved and new bonds are formed. The molecules which react in a chemical reaction are called reactants and the molecules produced in a reaction are called products. 

Introduction 

The scientist, Antonio Lavoisier, introduced the law of conservation of mass in the year 1789. According to him, mass can’t be destroyed or generated. But mass can be transformed from one form to another. In our daily life, we also utilize this law. For example, in the burning process of wood, the total masses of the products (gases, ashes, soot) and the masses of the reactants (charcoal and oxygen)remain the same. 

Define “The Law of Conservation Of Mass”:

This law states: “matter cannot be created or destroyed in a chemical reaction”. That means the total masses of reactants or products should be the same after a reaction.

Application of the law of conservation of mass in different reactions:

1. During phase transition: During the transformation of any substance from its solid to liquid and then to vapour, the total mass of the substance remains constant. In the physical change of ice to water and then water to vapour, the mass of water in its three states remains the same.

Ice ⇌ water ⇌ vapour

2. During chemical reaction: Total masses of the reactants and the products remain the same after a successful chemical reaction. Like, in the combustion reaction of methane, carbon dioxide \(C{O_2}\) and water \({H_2}O\) are produced. The total masses of reactants (\(C{H_4}\)and \({O_2}\)) remain the same as the masses of products (\(C{O_2}\) and \({H_2}O\)).

\[C{H_4} + 2{O_2} \to C{O_2} + 2{H_2}O\]

3. During rearrangement reaction: Calcium carbonate produces calcium oxide and carbon dioxide on heating. The masses of reactants (calcium carbonate) and the products (calcium oxide and carbon dioxide)remain the same.

\[CaC{O_3} \to {\rm{ }}CaO{\rm{ }} + {\rm{ }}C{O_2}\]

Methods to examine the law of conservation of mass:

1. In the reaction of Barium chloride and magnesium sulfate: The law of conservation of mass can be proved by the following reaction. For this, some steps need to be followed.

• First, a particular amount of Barium chloride (\(BaC{l_2}.2{H_2}O\)) is weighed. Then some amount of distilled water is mixed with it. And this mixture is named A.
• Then some definite amount of magnesium sulfate (\(MgS{O_4}\)) is mixed with the same amount of water as A. This mixture is indicated as B.
• Then another empty beaker(C) is taken and weighed. The whole solution of A and B is poured into beaker C.
• A white precipitate of \(BaS{O_4}\) is formed in beaker C. Then the weight of beaker C is taken again.
• Now the weight of empty beaker C is subtracted from the beaker C, containing products.
• Comparing the masses of A, B, and C, we get that the total masses of the solutions A and B match with the product formed in beaker C.

In this way, the conservation of mass can be proved.

\[BaC{l_2} + {\rm{ }}MgS{O_4} \to {\rm{ }}BaS{O_4} + {\rm{ }}MgC{l_2}\]

2. In the reaction of silver nitrate and sodium chloride: This law can be proved by the following reaction of silver nitrate and sodium chloride. For this, the following steps need to be followed.

• Silver nitrate and sodium chloride solutions are made separately. Sodium chloride solution is taken in a conical flask and silver nitrate is taken in an ignition tube.
• Then the ignition tube is suspended into the flask and the flask is fitted with a cork.
• Now the mass of the conical flask is recorded, and then the conical flask is tilted for the reaction of silver nitrate and sodium chloride.
• Now, the product \(AgCl\) is precipitated as a solid. At this stage, the mass of the conical flask is recorded again.
• It is found that the masses of reactants and products are the same.

\[NaCl{\rm{ }} + {\rm{ }}AgN{O_3} \to {\rm{ }}AgCl{\rm{ }} + {\rm{ }}NaN{O_3}\]

Summary

The law of conservation of mass tells us that the mass of reactants and products is always the same after a reaction. That is, the total mass is always conserved in different types of chemical reactions as well as in physical changes. This law can be proved by some reactions in the laboratory. This law is very essential as the unknown mass of any reactant or product can be determined. From this law, any chemical reaction can be balanced easily.

Frequently Asked Questions

1. What are the drawbacks of the law of conservation of mass?

Ans: This law is valid for only chemical reactions and physical changes. But does not apply to nuclear reactions. During a nuclear reaction, heat is produced. That means some mass is converted to heat. So the mass is not conserved in the nuclear reaction.

2. Is there any difference between the conservation of mass and the conservation of energy?

Ans: Conservation of mass and energy were commonly considered to be separate concepts. However, special relativity demonstrates that mass and energy are linked by the formula \(E{\rm{ }} = {\rm{ }}m{c^2}\), and science currently holds the belief that the sum of mass and energy is conserved.

3. Which equation corresponds with the principle of mass conservation?

Ans: The law of mass conservation can be expressed by a balanced chemical equation. In a balanced chemical equation, the number of each element involved in a reaction is always the same on the reactants and products side.

An introduction to Molecules

Atoms are the building blocks of all living things on this planet. An atom is the smallest unit that makes up a chemical element. Atoms make up everything else that is solid, liquid, or gas. Atoms are made up of protons, neutrons, and electrons that are contained within the nucleus of an atom. What happens when two or more atoms collide? They combine to form molecules. Molecules are formed when two or more atoms form chemical bonds with one another. Understanding the properties and structure of atoms and molecules is not easy, but once understood, it is a fascinating subject to study.

What are Molecules?

Elements are created when the same types of atoms combine. The number of atoms that make up a molecule has the same ratio. The structure of elements determines their properties. Elements can be made up of one or more atoms. Take, for example, oxygen, which has two atoms (\({O_2}\)). Atoms are not depicted to scale. A compound is formed when these elements are combined. We can use \({H_2}O\) in this case. Water contains two hydrogen atoms and one oxygen atom. Similarly, larger chemical compounds such as methane (\(C{H_4}\)). We can learn from these how a group of atoms with a nucleus can form elements and compounds with various properties and structures.

What is the difference between Atoms and Molecules?

Atoms	Molecules
Atoms are the smallest particle that can exist.	Two or more atoms combined to form molecules.
Atoms may not be stable due to the presence of electrons in the outer shells.	Molecules attain stability.
They contain protons, neutrons, and electrons.	Two or more atoms are formed and hence, they are strong.
Examples: Oxygen (O), phosphorus (P), sulphur (S) etc.	Examples: Oxygen (O2), water (H2O), and sulphur (S8).

Summary

Elements can be single atoms, such as He, or elemental molecules, such as hydrogen (\({H_2}\)), oxygen (\({O_2}\)), chlorine (\(C{l_2}\)), ozone (\({O_3}\)), and sulphur (\({S_8}\)). Atoms are not depicted to scale. Some elements are monatomic, which means that their molecular form is made up of a single (mono-) atom (-atomic).

Frequently Asked Questions (FAQs)

1. What do you understand by the Law of Conservation of Mass?

Ans: According to this law, “Mass can neither be created nor destroyed.” This law can be applied to a chemical reaction in the following way:- During a chemical reaction, the total mass of reactants equals the total mass of products.

\[\left( {Reactant} \right){\rm{ }}A + B{\rm{ }} \to {\rm{ }}AB{\rm{ }}\left( {Product} \right)\]

2. What is an atom?

Ans. According to modern atomic theory, an atom is the smallest particle of an element that participates in a chemical reaction and retains its identity throughout the chemical or physical change.

3. What do you understand by the Law of Constant Proportion?

Ans. According to this law, “A pure chemical compound always contains the same elements combined in the same proportion by mass, irrespective of the fact from where the sample has been taken or from which procedure has it been produced.”