Law of Mass Conservation Quiz

What does the conservation law of mass state?

• The mass of a closed system remains constant over time.

• All elements have the same mass.

• The total amount of energy in a system remains the same.

• The pressure & volume of a gas are proportional with constant temperature.

Who established and popularized the conservation law of mass in 1789?

• Antoine Lavoisier
• Hans Henrich Landolt

• Albert Einstein
• Niels Bohr

True or False: Before Lavoisier, the Ancient Greeks had already known that matter could not be created or destroyed.

• True

• False

Name what is NOT an example of how the conservation law of mass works.

• Burning wood: the mass of the wood is the same after turning to ash.

• Evaporation: as water evaporates, H2O molecules disperse into air.

• Rusting iron: iron and oxygen become iron oxide, but mass remains the same.

• Melting ice: the ice still has the same mass after melting into water.

Answer explanation

Reason: The law of conservation of mass states that the mass of a closed system remains constant over time. However, when water evaporates into water vapor, it loses mass and therefore, the mass does not remain the same.

True or False: Hans Hendrich Landolt supported Lavoisier's theory of mass conservation.

• True

• False

Through the Haber process, 34g of ammonia were produced. If there are 28g of nitrogen gas, what is the mass of hydrogen used?

• 4g
• 10g
• 8g
• 6g

28g of CO reacted with 4g of 2H₂ to produce 32g of CH₃OH. Find the percentage of carbon of the product!

• 30%

• 25%

• 37.5%

• 42.9%

Explain an example of how to calculate the mass of a product from the masses of the reactants.

Answer explanation

Because the mass of the reactant is the same as the mass of the product, the mass of the product is the sum of the masses of the reactants.

Explain whether or not the law of conservation of mass implies that mass can be created in a chemical reaction.

Answer explanation

According to the law of conservation of mass, mass cannot be created or destroyed, but it can be converted in a chemical way.

In a closed system, if 10g of substance A reacts with 5g of substance B, what is the total mass of the products? Explain!

Answer explanation

Remember: the sum of the mass of the reactants is always the same as the sum of the mass of the products.