Law of Conservation of Mass and Balancing Chemical Equations

Matter can not be created nor destroyed: it can only be

• Destroyed a little bit
• Invisible
• Transformed, changed
• None of the above

If reaction starts with 20g of reactants it should produce 

• a total of 40g of products
• a total of 10g of products
• a total of 80 g of products
• a total of 20g of products

Which of the models of a chemical reaction best represents the Law of Conservation of Mass?

• A

• B

• C

• D

A student heated a 10 gram sample of a chemical in an open container. A chemical reaction occurred, and the mass of the sample was measured again. The mass of the sample was found to be less than before the reaction. Which of the following best explains the decrease in mass of the sample?

• The heat caused the chemical to become less dense.

• The reaction gave off more heat than was added.

• Some of the lighter particles were destroyed.

• Some of the particles escaped as a gas formed.

A student dissolved 25 grams of salt into 1,000 grams of water. What should the mass of the saltwater mixture be?

• 975 grams

• 1,000 grams

• 1,025 grams

• 2,500 grams

What is the left part of a chemical equation called?

2H₂ + O₂ ---> 2H₂O

• Reactants

• Yields

• Products

• Chemical equation

What is the right part of a chemical equation called?

2H₂ + O₂ ---> 2H₂O

• Reactants

• Yields

• Products

• Chemical Equation

How many Mn atoms are found in the following compound?

2MnO₄

• 1

• 2

• 4

• 8

What is the little number after an element in a chemical equation called?

Example: H₂

• Coefficient

• Atom

• Subscript

• Equation

Is the following equation balanced?

Al + O₂ ---> 2Al₂O₃

• YES

• NO