Law of Conservation of Mass: Overview, Questions, Preparation

Q: Q: What is the importance of the law of conservation of mass?

A: The study and production of chemical reactions. By using this law, you can calculate the quantities of reactants and products. Manufacturers can increase efficiency by applying the law to their laboratory practices.

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Laws of Physics Law of Conservation of Mass Biot Savart Law Ideal Gas Law Radioactive Decay Law Continuity Equation Charge Definition Mach Number Chandrasekhar Limit Poissons Ratio Stefan Boltzmann Law Stokes Law Derivation Vectors Orbit and Orbital Sound Definition Quantum Number Definition Thermonuclear Reaction Time Period of Simple Pendulum ...

Rajdeep Das

Updated on Aug 16, 2021 06:00 IST

Table of Contents

Introduction
Law of Conservation of Mass
Activity to prove the law of conservation of mass
Law of Conservation of Mass for Class 11
Illustrated Examples

Introduction

We have studied that atoms can be neither created nor destroyed during a chemical reaction. The number of atoms remains the same before and after the chemical reaction. If the number of atoms does not change, then the chemical reaction can never change the mass. This observation leads to the law of conservation of mass.

Law of Conservation of Mass

It states that matter can neither be created nor destroyed in a chemical reaction. It is one of the laws of chemical combination. It means the total mass of reactants in a chemical reaction will equal the products' total mass. But there can be a change in form to other substances like gas, liquid, and solids. This law formed the basis of several practical developments in chemistry.

Activity to prove the law of conservation of mass

Place a beaker on a weighing balance and tare the balance. Take 1.5ml of calcium chloride solution in a test tube and place it in the beaker.
Add 1.5ml of sodium sulfate solution into the beaker and close the beaker with the cork.
Weigh the beaker's contents carefully, and tilt and swirl the flask so that the solutions get mixed.
The resultant mixture is the calcium sulfate precipitate in sodium chloride solution.
Now weigh the beaker and determine the mass. You will observe that the mass does not change upon the chemical reaction.

Law of Conservation of Mass for Class 11

This unit will help you understand basic chemistry concepts like laws of chemical combination, stoichiometric calculations, molarity, molality, moles, and molecular mass. This topic has less weightage when compared to the rest of the topics in this chapter. Short-answer questions worth 2-3 marks may be asked.

Illustrated Examples

5 grams of hydrogen reacts with oxygen to make 30 grams of water. Apply the law to calculate how much oxygen is required.

Mass of reactants = mass of products

Hydrogen +oxygen = Water

5+O = 30

So, 25 g of oxygen is required.

On heating, 10.0 grams of sodium carbonate (Na2CO3), 4.4 g of carbon dioxide (CO2) and 5.6 g of sodium oxide (Na2O) is produced. Show that this reaction obeys the law of conservation of mass.

Mass of reactants = mass of products

10.0 g of Sodium carbonate = 4.4 g of CO2+ 5.6 g of Sodium oxide

10 g of reactant = 10 g of product

How many grams of sodium carbonate are produced if 224.4 g of NaOH reacts with 88.0 g of CO2? The reaction produces 36.0 g of water.

Reactants mass = Product mass

4g NaOH + 88.0 g CO2 = Na2CO3+ 36.0g H20

276.4 g of sodium carbonate

FAQ's

Q: What are other laws of chemical combination?

A: The other laws of chemical combination are the law of multiple proportions, law of definite proportions, Gay Lussac's law and Avogadro law.

Q: Can the law of conservation of mass be violated?

A: Nuclear reactions violate the law of conservation of mass because mass is converted into energy.

Q: Explain the situations where the mass of reactants and products are not equal?

A: Experiments in which mass changes:

Reactions that do not go to completion give false results. If the reaction involves gas or gas is produced, then calculating a gas's mass is difficult.
There is no way to measure the mass of gaseous products lost to the air, unless you collect the air in sealed bags or balloons to preserve the mass.

Q: What is the importance of the law of conservation of mass?

The study and production of chemical reactions.
By using this law, you can calculate the quantities of reactants and products.
Manufacturers can increase efficiency by applying the law to their laboratory practices.

Q: Who founded the law of conservation of mass?

A: The law of conservation of mass was founded by French chemist Antoine Lavoisier in 1789 after performing experimental studies for combustion reactions.