Balancing Equations

Which problem is balanced?

• PbO₂ + 2H₂--> H₂SO₄
• SO₂ + H₂0 --> H₂SO₄
• 2Na + 2H₂O --> 2NaOH + H₂
• 2Na + 2H₂O --> 2NaOH + H

What is a coefficient?

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

Balance this equation
_Zn+_HCl-->_ZnCl₂ +_H₂

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

Balance this equation.
_Mg + _Cl₂ --> _MgCl₂

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

Balance this equation
_N₂ + _H₂ --> _NH₃

• 1,2,3
• 1,3,2
• 1,1,2
• 2,1,1

How many atoms of aluminum are on each side of the following equation: 4Al + 3O₂ --> 2Al₂ O₃

• 2
• 6
• 1
• 4

Number of H in 3(NH₄)₂CrO₄

• 4
• 6
• 8
• 24

At the end of chemical reactions, what is the total mass of the reactants compared to the total mass of the products?

• the product is doubled
• the product is half the mass of the reactants
• the mass is the same
• the mass changes depending on the reaction

Balance this equation:
P₄+O₂  -->  P₂O₃

• 3 P₄+ O₂ --> 2 P₂O₃
•  P₄+ O₂ --> 2 P₂O₃
•  P₄+ 3 O₂ --> 2 P₂O₃
•  P₄+ 2 O₂ --> 3 P₂O₃

Which elements are(is) not balanced?
LiNO₃ +CaBr₂ --> Ca(NO₃)₂ +  LiBr   

• Li
• Ca and Li
• O and N
• Ca