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Law of conservation of mass states that mass can neither be created nor destroyed. It means that during the chemical reaction mass of an element will remain the same throughout the procedure. According to law of conservation of mass, “Any isolated system’s mass can neither be created nor be destroyed, but can be changed from one form to another.” As per law of conservation of mass, the mass of the reactants should be equivalent to the mass of the products for a low-energy thermodynamic process.
Read More: Conservation Laws in Physics
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Key Terms: Mass, Reactant, Energy, Product, Chemical Reactions, Chemical Reaction, Physical Transformation, Combustion
What is Law of Conservation of Mass?
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According to the law of conservation of mass, the mass of the reactants should always be equal to the mass of the products.
Examples of Law of Conservation of Mass
Some examples of the Law of Conservation of Mass include:
- Combustion Process: the burning of wood comes under conservation of mass because it involves carbon dioxide, ashes, oxygen, and water vapour.
- Chemical Reactions: to evaluate one molecule of H2O with the molecular weight of 10, molecular weight with 2 of hydrogen is added with oxygen with a molecular weight of 8, hence, it conserves the mass.
Also Read: Laws of Chemical Combinations
Solved ExampleQues. 10 grams of calcium carbonate (CaCO3) can generally yield 3.8 grams of carbon dioxide (CO2) and 6.2 grams of calcium oxide (CaO). Signify this reaction in terms of law of conservation of mass. Ans. As per the law of conservation of mass, it can be said that, Mass of reactants = Mass of products Therefore, 10 gram of CaCO3 = 3.8 grams of CO2 + 6.2 grams of CaO Thus, 10 grams of reactant will be equal to 10 grams of products. \(\therefore\) 10 grams of reactant = 10 grams of products Hence, it’s proved that the law of conservation of mass has been followed by the given equation. |
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| Important Topic Related Links | ||
|---|---|---|
| Laws of Chemical Combination | Displacement Reactions | Mass and Momentum |
Formula Of Law Of Conservation Of Mass
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The formula of the law of conservation of mass is:
| ∂p / ∂t + ⛛ (pv) = 0 |
Where:
- ρ = density
- t = time
- v = velocity
- ⛛ = divergence
Law of Conservation of Mass
The formula of the law of conservation of mass says that the total mass of products in a chemical reaction is equal to the mass of reactants.
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Things To Remember
- Combustion process and the chemical process is examples of the law of conservation of mass.
- In the law of conservation of mass matter is neither created nor destroyed.
- It also states that the total mass of products in a chemical reaction is equal to the mass of reactants.
- The law of conservation of mass was studied in 1789 by French chemist Antoine Lavoisier.
Read More: Conservation of Energy Formula
Sample Questions
Ques. Define the law of conservation of mass. (2 Marks)
Ans. The Law of conservation of mass was studied in 1789 by French chemist Antoine Lavoisier. The law of conservation of mass states that mass in any closed or isolated system remains the same, it can neither be created nor destroyed by any physical transformation or chemical reactions but can be transformed.
The law of conservation of mass also states that the mass of the reactants should always be equal to the mass of the products.
Ques. What are the examples of the law of conservation of mass? (2 Marks)
Ans. Examples are:
- Combustion process: the burning of wood comes under conservation of mass because it involves carbon dioxide, ashes, oxygen, and water vapour.
- Chemical reactions: to evaluate one molecule of H2O with the molecular weight of 10, molecular weight with 2 of hydrogen is added with oxygen with a molecular weight of 8, hence, it conserves the mass.
Ques. What is the law of conservation of mass state? (1 Mark)
Ans. During a chemical reaction between objects, the mass produced by them is neither created nor destroyed. And the carbon atom changes from a complex solid structure to a simple gas yet the mass is the same.
Ques. What is the other name for the law of conservation of mass? (1 Mark)
(a) Law of mass and conservation
(b) Law of mass action
(c) Law of indestructibility
(d) Law of chemical reaction
Ans. c. Law of indestructibility
Explanation: The law of conservation of mass is also known as the law of indestructibility
Ques. Why can't we observe any changes in mass during chemical reactions? (1 Mark)
Ans. We can’t observe any changes in mass during a chemical reaction because atoms can neither be created nor be destroyed. The atoms in reactants are only rearranged to form products. Hence, there are no changes.
Ques. What is the formula for the law of conservation of mass? (2 Marks)
Ans. The formula of law of conservation of mass is
∂p / ∂t + ⛛ (pv) = 0
Where;
ρ = density
t = time
v = velocity
⛛ = divergence
Ques. What are the significances of the law of mass conservation? (3 Marks)
Ans. The significance of the law of mass conservation are:-
- WIth putting on to law on laboratory practices, manufacturers can increase their efficiency.
- The creations of chemical reactions
- The investigation of chemical reactions
- The reaction is used to evaluate the quantities of products and reactants.
Ques. Why is the law of conservation of mass only applicable to chemical changes? (2 Marks)
Ans. The law of conservation of mass states that mass in any particular isolated/closed system can neither be created nor destroyed by any chemical reactions or physical transformations. According to the law of conservation of mass, the mass of the reactants should always be equal to the mass of the products. Thus the law of conservation of mass applies only to chemical changes that evolve.
Ques. 6 grams of hydrogen reacts with oxygen to make 40 grams of water. Evaluate the amount of oxygen used by using the law of conservation of mass. (3 Marks)
Ans. As we know;
Hydrogen + Oxygen = Water
Given;
Hydrogen - 6 grams
Water - 40 grams
Oxygen - to find
Let oxygen be - x
According to the law of conservation of mass
Mass of reactants = Mass of products
6g + x g = 40g
x g = 40g - 6g
x = 34g
x = oxygen = 34g
Ques. The mass of the reactants should always be equal to the mass of the (1 Mark)
(a) Energy
(b) Products
(c) Reaction
(d) None of the above
Ans. b. Products
Explanation: The law of conservation of mass states that the mass of the reactants should always be equal to the mass of the products. This law of conservation of mass was studied in 1789 by French chemist Antoine Lavoisier.
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