CHEMICAL REACTIONS

When two or more elements or compounds combine together to form new compounds with different properties a

chemical reaction has occurred

• Chemical reactions are written using a chemical equation• 2Mg + O2 2MgO

“yields”

reactants products

Law of Conservation of Mass

The mass of the products MUST be equal to the mass of the reactants.

When you write a chemical equation, you MUST observe the law of conservation of mass –

the equation MUST be balanced

2Mg + O2 2MgO

Mg – 2 Mg – 2 O – 2 O – 2

Br2 + NaI I2 + NaBr

Br – 2 Br -1 NO! Na – 1 Na – 1 I – 1 I - 2

YES!

Is this chemical equation balanced?

Na + AlCl3 NaCl + Al

Is this chemical equation balanced?

KBr + Cl2 KCl + Br2

Is this chemical equation balanced?

H2O2 H2O + O2

Balance these chemical equations:

N2 + H2 NH3

KClO3 KCl + O2

NaCl + F2 NaF + Cl2

H2 + O2 H2O

Pb(OH)2 + HCl H20 + PbCl2

Balance these chemical equations:

AlBr3 + K2SO4 KBr + Al2(SO4)3

CH4 + O2 CO2 + H2O

C3H8 + O2 CO2 + H2O

CO2 + H2O C6H12O6 + O2

C8H18 + O2 CO2 + H2O