Chapter 3 Stoichiometry

Stoichiometry – built on the law of conservation of mass (Antione Lavasier) His ideas flowed from the work on the atomic theory – atoms: neither created nor destroyed in a chemical reaction.

Example: C3H8 + __O2  __CO2 + __H2O Balancing Equations You can only change coefficients! Example: C3H8 + __O2  __CO2 + __H2O 5 3 4

Chemical reactions – some examples Combustion:  A + B ---> AB 8 Fe + S8 ---> 8 FeS  Decomposition:  AB ---> A + B 2 H2O ---> 2 H2 + O2  Single Replacement: A + BC ---> AC + B Mg + 2 H2O ---> Mg(OH)2 + H2

Double Replacement: Acid-base: Combustion: AB + CD ---> AD + CB Pb(NO3)2 + 2 KI ---> PbI2 + 2 KNO3  Acid-base: HA + BOH ---> H2O + BA HBr + NaOH ---> NaBr + H2O  Combustion:  C10H8 + 12 O2 ---> 10 CO2 + 4 H2O

1)  NaOH + KNO3 --> NaNO3 + KOH 2)  CH4 + 2 O2 --> CO2 + 2 H2O 3)  2 Fe + 6 NaBr --> 2 FeBr3 + 6 Na 4)  CaSO4 + Mg(OH)2 --> Ca(OH)2 + MgSO4 5)  NH4OH + HBr --> H2O + NH4Br 6)  Pb + O2 --> PbO2 7)  Na2CO3 --> Na2O + CO2

1)  double replacement  2)  combustion  3)  single replacement  4)  double replacement  5)  acid-base  6)  synthesis  7)  decomposition

Molecular Mass is total mass of all the atoms in a molecule Formula mass is the mass of a unit cell in an ionic compound.

Percent Composition AW stands for the atomic weight of the atom from the periodic table. FW stands for the formula weight of the compound.

The mole Based on the work of Avogadro Molar mass is the weight of one mole (or 6.02 x 1023 molecules) 1 mole Al - 6.02 x 1023 atoms 1 mole CaCl2 - 6.02 x 1023 molecules The molar mass of elements is found by looking at the atomic mass of the element on the periodic table (for cmpds some all atoms)

Empirical Formula Molecular Formula Hydrates Combustion Analysis

Stoichiometry Conversions- (gram to gram)

Limiting Reactants The reactant that is consumed – all of it used up in the reaction Chapter 3

Theoretical Yields The amount of product predicted from stoichiometry taking into account limiting reagents is called the theoretical yield. The percent yield relates the actual yield (amount of material recovered in the laboratory) to the theoretical yield: Chapter 3