Question

a. breaking an ice cube
b. melting gold
c. running an electric current through copper
d. corroding iron

1. which of the following is true for all chemical reactions?

a. the total mass of the products is greater than the total mass of the reactants.
b. the total mass of the reactants increases.
c. the total mass of the products is less than the total mass of the reactants.
d. the total mass of the reactants equals the total mass of the products.

1. which statement is true about compounds?

a. they can be separated by physical means
b. they are made of only one type of atom
c. they are chemically combined substances
d. they always exist in solid state

Explanation:

Question 49

To solve this, we recall the Law of Conservation of Mass, which states that in a closed system, the mass of reactants equals the mass of products in a chemical reaction.

• Option a is wrong because products' mass isn't greater.
• Option b is wrong as reactants' mass doesn't increase.
• Option c is wrong as products' mass isn't less.
• Option d follows the Law of Conservation of Mass.

We analyze each option based on the definition of a compound:

• Option a: Compounds are chemically combined, so physical means can't separate them (mixtures can be physically separated). So a is wrong.
• Option b: Compounds are made of two or more different atoms (elements have one type). So b is wrong.
• Option c: Compounds are substances where elements are chemically combined. This matches the definition.
• Option d: Compounds can be solid, liquid, or gas (e.g., water is liquid, carbon dioxide is gas). So d is wrong.

Answer:

d. The total mass of the reactants equals the total mass of the products.

Question 50