Balancing Equations

What does the Law of Conservation of Mass state?

• Matter cannot be gained or lost in a chemical reaction.
• Matter can only be lost in a chemical reaction.
• Matter can only be gained in a chemical reaction.
• Matter can be gained and lost in a chemical reaction. 

Is this balanced?...
Fe + S --> FeS

• YES!
• NO!

What is a coefficient?

• The small number on the right of the chemical symbol.
• The large number to the left of a formula.

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

• Yes
• No

Balance this equation-
__P₄ + __O₂ --> __P₂O₃

• it is already balanced
• 2, 1, 3
• 1, 2, 3
• 1, 3, 2

Balance this equation.
_CH₄ + _O₂ --> _CO₂ + _H₂O

• 1,2,1,1
• 2,1,2,1
• 1,2,1,2
• 0,2,0,2

Balance this equation.
_Mg + _Cl₂ --> _MgCl₂

• 1, 2,1
• already balanced
• 2,1,1
• 1,1,2

What is the little number after an element in a chemical equation called.
Example: H₂

• Coefficient 
• Subscript
• Atom
• Equation

KNO₃ --> KNO₂ + O₂
What coefficients are needed to balance the reaction?

• 2, 2, 1
• 2, 3, 2
• 1, 2, 2
• 1, 3, 1

Which side of a chemical equation is the product side?

• Left (before the arrow)
• Right (after the arrow)