Unit 3: Chemical Equations and Stoichiometry Balancing Equations

Balancing Equations reactants  products Remember the law of conservation of mass? When a chemical reaction occurs, no atoms are created or destroyed – they are just rearranged Amount of each element on the left side (reactants) must equal the amount of the same element on the right side (products) reactants  products

Balancing Equations – The Steps! Put coefficients in front of each substance to get the quantities on the left side = the right side 2Na + Cl2  2NaCl Use the smallest whole number coefficients possible.

Balancing Equations - Hints Start with one of each reactant and product. Save hydrogen for 2nd to last. Save oxygen for last. Diatomic elements: HOFBrINCl (only when alone) Example: hydrogen gas is written H2 Phases: Solid = (s) Liquid = (l) Gas = (g) Aqueous (dissolved in water or solution) = (aq)

Balancing Equations Example #1 Now let’s balance this equation… __C3H8 (g) + __O2 (g)  __CO2 (g) + __H2O (l)

Balancing Equations Practice #1 Balance the following chemical equation: __PbS2 (s) + __O2 (g)  __PbO2 (s) + __SO2 (g)