Download Chem Catalyst

Chem Catalyst
Calculate the percent composition of
ibuprofen (C13H18O2)
Today’s Agenda:
Catalyst
2. Finish Notes- Empirical Formula
3. Practice Problems
4. HW: p. 312 #45-46
1.
Chemical Formulas:
Empirical formula: the lowest whole-number ratio
of the atoms of elements in a compound
Molecular formula: the exact number of atoms of
elements in a compound
For example, styrene (C2H2), and acetylene (C8H8)
have different molecular formulas but the same
empirical formula (CH)
Finding Empirical Formulas:
Determining the MOLE RATIO of elements in a
compound.
1. Find percent composition (if not given)
2. Divide percent composition by molar mass of
element to get mole ratios
3. Simplify to whole numbers by dividing all mole
ratios by the smallest one
4. Write the formula with the subscripts
Empirical Formula: Example
A compound contains 25.9% nitrogen, and 74.1%
oxygen. What is the empirical formula of this
compound?
Empirical Formula: Example
Calculate the empirical of these compounds:
1) 94.1% O, 5.9% H
2) 67.6% Hg, 10.8% S, 21.6% O
Molecular Formula: Example
A compound has an empirical formula CH and a
molar mass of 104.2 g/mol. What is its molecular
formula?
1. Divide the molar mass of the empirical formula
by molar mass of the molecular formula.
2. Multiply all subscripts by that value.
Molecular Formula: Example
A compound has an empirical formula CH and a
molar mass of 104.2 g/mol. What is its molecular
formula?
Empirical Formula: Example
Calculate the empirical formula of these
compounds:
3) 36.1% Ca, 63.9% Cl
2) 40.0% C, 6.7% H, 53.3% O