HUKUM KEKEKALAN MASSA ( HUKUM LAVOISIER ) : HUKUM DASAR KIMIA

Summary

This video explains the Law of Conservation of Mass through real-life examples and experiments. The law, established by Lavoisier, states that the mass of substances before and after a chemical reaction remains constant. Examples include the burning of paper, rusting of iron, and the reaction of lead nitrate with potassium iodide. The video also covers practical calculations and how mass is conserved in various reactions. Viewers will understand how to apply this principle in chemical equations and experiments, reinforcing the importance of this foundational law in chemistry.

Takeaways

• 😀 The Law of Conservation of Mass states that in a closed system, the mass of substances before and after a chemical reaction remains the same.
• 😀 The concept was developed by Antoine Lavoisier through careful experiments, which showed that mass is neither created nor destroyed in chemical reactions.
• 😀 In the example of paper burning, the mass of the ash is lighter than the original paper because the gaseous products escape into the air and are not measured.
• 😀 In the example of rusting iron, the mass of iron increases as it reacts with oxygen from the air to form iron oxide (Fe₂O₃), showing a gain in mass.
• 😀 The Law of Conservation of Mass is demonstrated through controlled experiments where the mass before and after the reaction in a closed system remains constant.
• 😀 A specific experiment using lead(II) nitrate and potassium iodide solutions in a sealed tube shows that the mass before and after the reaction is the same.
• 😀 The mass change in reactions is often due to whether the reaction occurs in an open or closed system, which can lead to gas escape or absorption.
• 😀 Chemical reactions like the formation of iron oxide during rusting result in a mass increase because oxygen from the air combines with the metal.
• 😀 Multiple-choice questions at the end of the video test the understanding of the Law of Conservation of Mass by asking about the mass relationship in various reactions.
• 😀 Understanding the law is crucial in predicting and analyzing chemical reactions, as it helps us anticipate how matter behaves during transformations.

Q & A

What is the law of conservation of mass, and who discovered it?

The law of conservation of mass states that the mass of substances before and after a chemical reaction remains the same in a closed system. This law was discovered by Antoine Lavoisier.

What happens during the combustion of paper in an open environment according to the law of conservation of mass?

During the combustion of paper in an open environment, the mass of the ashes produced is lighter than the original mass of the paper. This is because the gases produced during the reaction escape into the air, and are not measured, leading to a decrease in the observed mass.

How does the rusting of iron follow the law of conservation of mass?

When iron rusts, it reacts with oxygen in the air to form iron oxide. The mass of the iron after rusting is heavier than the initial mass because the iron combines with oxygen from the air, which adds mass to the resulting iron oxide.

Why is the law of conservation of mass not followed in the combustion of paper in an open system?

The law of conservation of mass is not followed in the combustion of paper in an open system because gases released during the reaction, such as carbon dioxide and water vapor, are not captured. As a result, the total mass of the system appears to decrease.

What is an example of a chemical reaction where the law of conservation of mass holds true?

An example is the reaction between lead(II) nitrate (Pb(NO3)2) and potassium iodide (KI). When mixed in a closed container, the total mass of the reactants before the reaction equals the total mass of the products after the reaction.

How can you experimentally demonstrate the law of conservation of mass?

You can demonstrate the law of conservation of mass by performing an experiment where you react two substances in a closed container, such as mixing lead(II) nitrate and potassium iodide, and measure the total mass before and after the reaction. The mass should remain the same.

What does the equation Pb(NO3)2 + 2KI → PbI2 + 2KNO3 illustrate?

This equation illustrates a chemical reaction where lead(II) nitrate and potassium iodide react to form lead(II) iodide and potassium nitrate. According to the law of conservation of mass, the mass of the reactants equals the mass of the products in a closed system.

Why does the mass of iron increase during the rusting process?

The mass of iron increases during the rusting process because iron reacts with oxygen in the air to form iron oxide (Fe2O3), which adds the mass of oxygen to the iron.

What happens if the law of conservation of mass is violated in a chemical reaction?

If the law of conservation of mass appears to be violated, it often means that some of the reactants or products, such as gases or volatile compounds, have escaped or were not measured correctly, leading to an incorrect measurement of mass.

How do we apply the law of conservation of mass to solve chemical problems?

The law of conservation of mass is applied by ensuring that the mass of the reactants equals the mass of the products in any chemical reaction. This principle is used to calculate unknown quantities, such as the mass of a product or the amount of a reactant needed.