The law of conservation of mass states that mass cannot be created or destroyed in a chemical reaction; it can only change forms. This principle is fundamental in chemistry and helps us understand how substances interact during reactions. Among the options you've provided, the best example of the law of conservation of mass is option A: "12 gm of carbon combines with 32 gm of oxygen to form 44 gm of CO2." Let's break this down further to clarify why this is the correct choice.
Understanding the Options
To determine which example best illustrates the law of conservation of mass, we need to analyze each option:
- Option A: 12 gm of carbon combines with 32 gm of oxygen to form 44 gm of CO2.
- Option B: When 12 gm of carbon is heated in a vacuum, there is no change in mass.
- Option C: A sample of air increases in volume when heated at constant pressure, but its mass remains unaltered.
- Option D: The weight of a piece of platinum is the same before and after heating the air.
Analyzing Each Example
Let's look at each option in detail:
Option A: A Clear Example
This scenario perfectly illustrates the law of conservation of mass. Here, the total mass of the reactants (12 gm of carbon + 32 gm of oxygen) equals the mass of the product (44 gm of CO2). This demonstrates that mass is conserved during the chemical reaction, as the total mass before the reaction is equal to the total mass after the reaction.
Option B: No Change in Mass
While this option indicates that mass remains unchanged, it does not involve a chemical reaction. Instead, it describes a physical process where carbon is heated in a vacuum. The law of conservation of mass applies to chemical reactions, so this example is not suitable.
Option C: Volume vs. Mass
This option discusses the behavior of air when heated, noting that its volume increases but its mass remains the same. Although it highlights a physical property, it does not demonstrate a chemical reaction, making it less relevant to the law of conservation of mass.
Option D: Consistency in Weight
This example shows that the weight of platinum remains unchanged before and after heating. However, it does not involve a chemical reaction or a transformation of substances, so it does not effectively illustrate the law of conservation of mass.
Conclusion
In summary, option A is the most appropriate example of the law of conservation of mass because it involves a chemical reaction where the total mass of the reactants equals the total mass of the products. This principle is crucial in understanding chemical processes and helps us predict the outcomes of reactions accurately. By recognizing how mass is conserved, we can better grasp the fundamental concepts of chemistry.
