Chemical Reactions The result of the chemical

reaction is a new substance with unique physical and chemical properties.

Na (s) + Cl2 (g) NaCl

Reactants Products

Skeletal equation

NaHCO3(s) + HCl(aq) NaCl(aq) + H2O(l) + CO2(g)

yield sign(aq) aqueous (dissolved in water)(s) Solid i precipitate (an insoluble

solid)(l) Liquid(g) or gas ∆ heat is added

Remember

2Al2O3

Coefficient SubscriptsCoefficients will multiply by the subscripts

To get total atoms of an element

Al=2x2= 4 atoms of Al

O=2x3= 6 atoms of O

Try Ca(NO3)2

How many Ca How many

NO3 How many N How many O

1 Ca (1x1) 2 NO3 (1X2) 2 N (1x2x1) 6 O (1x2x3)

Try 2Ca(NO3)2 How many Ca How many

NO3 How many N How many O

2 Ca (2X1) 4 NO3 (2x2) 4 N (2x2x1) 12 O (2x2x3)

Balancing equationsThe number of each element in the reactants must

equal the numbers of each element in the products.

Only change coefficients, NOT subscripts. H2(g) + O2(g) H2O(l)

2 H 2 2 O 1 H2(g) + O2(g) 2H2O(l)

2 H 4 2 O 2 2H2(g) + O2(g) 2H2O(l)

4 H 4 2 O 2

AgNO3 + H2S Ag2S + HNO3

1 Ag 2 1 N 1 3 O 3 2 H 1 1 S 1 2AgNO3 + H2S Ag2S + 2HNO3

Decomposition of hydrogen peroxide

H2O2(l) H2O(l) + O2(g)

Balanced: 2H2O2(l) 2H2O(l) + O2(g)

Stoichiometry

1 frame and 3 wheels are needed to create one tricycle

If I use 1 dozen frames , how many tricycles can I make?

If I use 1 dozen wheels, how many tricycles can I make?

1 dozen

4 or (1/3 dozen)

Stoichiometry

2AgNO3 + H2S Ag2S + 2HNO3

2 moles of silver nitrate yields 1 mole of silver sulfide

Conversion Factor: 2 mole AgNO3 = 1 mole Ag2S

2AgNO3 + H2S Ag2S + 2HNO3

How many moles of Ag2S will be produced from 3.5 moles of AgNO3

3.5 mole AgNO3 x 1 mole Ag2S = 1.75 mole Ag2S

2 mole AgNO3