Unit 2.2 Conservation of Mass Lesson

Law of Conservation of Mass

During chemical reactions, matter is neither created nor destroyed. It is only transformed from one form to another. Mass ALWAYS remains the same.

Multiple Choice

The Law of Conservation of Mass states Matter is NEITHER created nor destroyed.

• True

• False

Multiple Choice

The number in front of a compound or element is a 

• Subscript
• Coefficient
• Superscript
• Charge

Multiple Choice

The Coefficient (3) in the Chemical Formula, 3H₂O, tells you how many _____________ there are.

• Atoms of Hydrogen

• Atoms of Oxygen

• Atoms of Water

• Molecules of Water

Multiple Choice

What are the reactants in the following chemical equation?

• CH₄ and 2O₂

• CO₂ and 2H₂O

Multiple Choice

The number to the lower side of an element is a 

• Subscript
• Superscript
• Coefficient
• Charge

Multiple Choice

What are the products in the following chemical equation?

• CH₄ and 2O₂

• CO₂ and 2H₂O

Multiple Choice

How many oxygen atoms are in this chemical formula?

• 6 oxygen atoms

• 2 oxygen atoms

• 3 oxygen atoms

• 4 oxygen atoms

Balancing Chemical Equations

For an equation to be balanced, there needs to be the same number of atoms on both sides of the equation.

Multiple Choice

A chemical reaction is balanced when

• both sides have the same elements
• Both sides have the same  number of atoms
• Same subscripts
• Same coefficients

Multiple Choice

How many carbon atoms are on both sides of the equation?

• 1

• 2

• 3

Multiple Choice

If a reaction starts with a total 75g of reactants it should produce 

• a total of 40g of products
• a total of 75g of products
• a total of 180 g of products
• None of the above

Multiple Choice

How many hydrogen atoms are on both sides of the equation?

• 2

• 4

• 1

Multiple Choice

24 g of magnesium reacts with 38 g of fluorine to produce _____ g magnesium fluoride

• 62 
• 38
• 24
• 14

Multiple Choice

How many oxygen atoms are on both sides of the equation?

• 2

• 4

• 1

Multiple Choice

32 g of Oxygen completely reacts with 8 g of Hydrogen to produce _____ g Water

• 8

• 12

• 24

• 40

Multiple Choice

Is this a balanced equation?

• yes

• no

• huh...

Multiple Choice

What is the arrow in a chemical equation...
H_{2 +} O --> H₂O

• Reactants
• Products 
• Yields 
• Chemical Equation 

Multiple Choice

How many elements does PbNO₃ have?

• 2
• 3
• 4
• 5

Multiple Choice

How many nitrogen atoms does NH₃ have?

• 1
• 2
• 3
• 4

Multiple Choice

Which equation best represents the law of conservation of mass? 

• A
• B
• C
• D

Multiple Choice

Is this equation balanced or unbalanced?

CH₄ + 2O₂--> CO₂+ 2H₂O

• balanced

• unbalanced

Multiple Choice

12g of Carbon react with 16g of Oxygen, how much carbon monoxide (CO) is formed? 

• 28 g
• 4g
• 30g
• 12g

Multiple Choice

Is the equation balanced?: 2H₂O + O₂ --> 4MgO + 3Fe

• yes

• no

Multiple Choice

Is this equation balanced or unbalanced? 
H₂ + O₂ --> H₂O

• balanced
• unbalanced

Multiple Choice

Is the following equation balanced?

Al + O₂ ---> 2Al₂O₃

• YES

• NO

Multiple Choice

The following chemical equation IS NOT balanced. What coefficients would make it balanced?

___Al +___ O₂ ---> 2Al₂O₃

• 3 Al and 2 O

• 2 Al and 3 O

Multiple Choice

Balance this equation:

___H₂ +___ Cl₂ --->___ HCl

• It is balanced.

• H₂ + Cl₂ ---> 2HCl

• 3H₂ + Cl₂ ---> 6HCl

• H₂ + 3Cl₂ ---> 6HCl

Multiple Choice

How many HCl molecules do you need to balance this equation? 
Mg +  __HCl --->  MgCl₂ + H₂

• 1
• 2
• 3
• 4