Chapter 3 Stoichiometry Stoichiometry built on the law

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.

Balancing Equations • You can only change coefficients! 5 2 __CO 3 2 + __H 4 2 O Example: C 3 H 8 + __O

Chemical reactions – some examples • Combustion: – A + B ---> AB – 8 Fe + S 8 ---> 8 Fe. S • Decomposition: – AB ---> A + B – 2 H 2 O ---> 2 H 2 + O 2 • Single Replacement: – A + BC ---> AC + B – Mg + 2 H 2 O ---> Mg(OH)2 + H 2

• Double Replacement: – AB + CD ---> AD + CB – Pb(NO 3)2 + 2 KI ---> Pb. I 2 + 2 KNO 3 • Acid-base: – HA + BOH ---> H 2 O + BA – HBr + Na. OH ---> Na. Br + H 2 O • Combustion: – C 10 H 8 + 12 O 2 ---> 10 CO 2 + 4 H 2 O

• • 1) Na. OH + KNO 3 --> Na. NO 3 + KOH 2) CH 4 + 2 O 2 --> CO 2 + 2 H 2 O 3) 2 Fe + 6 Na. Br --> 2 Fe. Br 3 + 6 Na 4) Ca. SO 4 + Mg(OH)2 --> Ca(OH)2 + Mg. SO 4 5) NH 4 OH + HBr --> H 2 O + NH 4 Br 6) Pb + O 2 --> Pb. O 2 7) Na 2 CO 3 --> Na 2 O + CO 2

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 Ca. Cl 2 - 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 theoretical yield. • The percent yield relates the actual yield (amount of material recovered in the laboratory) to theoretical yield: Chapter 3