Chemistry Concepts Quiz

What does the law of conservation of mass state about the mass of substances before and after a chemical reaction?

• The mass is unpredictable after the reaction.

• The mass increases after the reaction.

• The mass decreases after the reaction.

• The mass remains the same before and after the reaction.

In the rusting example, what was the initial mass of the iron pot before rusting?

• 143 grams

• 101 grams

• 42 grams

• 200 grams

How much oxygen reacted with the iron to form rust in the given example?

• 0 grams

• 143 grams

• 101 grams

• 42 grams

What is another name for the law of definite proportion?

• Law of chemical change

• Law of mass conservation

• Law of constant composition

• Law of variable composition

Who was the first to discover the law of definite proportion?

• Aristotle

• Dalton

• Proust

• Lavoisier

What is the mass percentage of calcium in calcium carbonate according to the law of definite proportion?

• 12%

• 48%

• 60%

• 40%

How is the mass percent of an element in a compound calculated?

• By multiplying the mass of the element by the total mass of the compound.

• By subtracting the mass of the element from the total mass of the compound.

• By dividing the mass of the element by the total mass of the compound and multiplying by 100.

• By adding the mass of the element to the total mass of the compound.

What does the law of definite proportion suggest about the composition of substances?

• It changes with temperature.

• It is independent of the origin.

• It varies depending on the source.

• It depends on the method of extraction.

According to the law of definite proportion, how does a compound differ from a mixture?

• A compound has a fixed composition.

• A compound has a variable composition.

• A mixture has a fixed composition.

• A mixture is composed of only one element.

What was disproven by the law of definite proportion regarding Aristotle's theory?

• The theory of chemical reactions.

• The theory of atomic structure.

• The theory of four essences.

• The theory of mass conservation.