Which statement best represents the Law of Conservation of Mass?
Matter can disappear in a chemical reaction.
The total mass of substances stays the same a chemical reaction.
The mass of a substance increases during a physical change.
Mass conservation only applies to gases.
The total mass of substances stays the same in a chemical reaction.
are you sure
Yes, I am sure. The Law of Conservation of Mass states that in a closed system, the total mass of substances before and after a chemical reaction remains constant. Matter is neither created nor destroyed in a chemical reaction, only rearranged.
The statement that best represents the Law of Conservation of Mass is: "The total mass of substances stays the same during a chemical reaction."
To understand why this statement is true and aligns with the Law of Conservation of Mass, it is important to revisit the definition of this principle. The Law of Conservation of Mass states that, in a closed system, the mass of the reactants in a chemical reaction is equal to the mass of the products. In simpler terms, this means that matter cannot be created or destroyed during a chemical reaction.
To determine if the total mass of substances stays the same during a chemical reaction, you need to analyze the number and types of atoms present before and after the reaction. This can be done by balancing the chemical equation, which involves ensuring that the number of atoms of each element is the same on both sides of the equation.
By following the steps below, you can apply the Law of Conservation of Mass and prove that the total mass of substances does indeed remain constant in a chemical reaction:
1. Write down the balanced chemical equation for the reaction you are studying.
For example, let's consider the reaction between hydrogen gas (H₂) and oxygen gas (O₂) to form water (H₂O):
2H₂ + O₂ → 2H₂O
2. Determine the molar masses of each substance present in the balanced equation.
The molar mass of hydrogen gas (H₂) is 2 grams per mole (g/mol).
The molar mass of oxygen gas (O₂) is 32 g/mol.
The molar mass of water (H₂O) is 18 g/mol.
3. Multiply the molar mass by the stoichiometric coefficient for each substance (the number in front of each chemical formula) to find the total mass of each substance in the reaction.
In our example:
- The total mass of hydrogen gas (H₂) before the reaction is 2 * 2 = 4 grams.
- The total mass of oxygen gas (O₂) before the reaction is 1 * 32 = 32 grams.
- The total mass of water (H₂O) after the reaction is 2 * 18 = 36 grams.
4. Compare the total mass of the reactants to the total mass of the products.
Before the reaction: 4 grams (hydrogen) + 32 grams (oxygen) = 36 grams (total mass of reactants)
After the reaction: 36 grams (total mass of products)
As you can see, the total mass of the reactants (before the reaction) is equal to the total mass of the products (after the reaction). This verifies that the Law of Conservation of Mass holds true, and that the statement "The total mass of substances stays the same during a chemical reaction" accurately represents this fundamental principle.