Chapter 3: Stoichiometry

1 Mol=

6.022×10²³

Avogadro’s number

1 mol/6.022×10²³

1 mol of a compound=

molecule

1 mol of an element=

atoms

equation for atoms/molecules per element/compound

6.022×10²³ atoms (molecules)/1 mol element (compund)

Molecular weight formula

# grams/ 1 mol

mol of atom per element equation

subscript # mol atom/ 1 mol compound

Mol:Mol ratios

the only unit conversion between 2 different substances

Percent composition formula

MW of elemnts/MW of compound X 100

Empirical formula

simplest form or ratio

Molecular formula

actual number of each element present

Finding Molecular Formula from Empirical formula

MW of MF/EW of EF=Factor

Factor X EF=MF

Steps for elemental analysis

1. change % to grams

2. convert grams to moles

3. divide moles by smallest number of moles to get a ratio

4. If all numbers are not whole numbers, multiply by appropriate fraction to eliminate decimals

5. Write EF from whole number ratio

6. Multiply EF by factor to get MF

Combustion analysis steps

1. convert grams of each oxide into moles of oxide

2. convert moles of oxide to moles of original element

3. convert moles of element to grams

4. subtract the sum of the grams from the total sample mass

5. Now that all elements are known, convert grams back to moles of that element

6. Divide all moles by smallest mole to get a ratio

7. If decimal, multiply by appropriate fraction

8. Write EF from whole number ratio

9. Find MF

When balance leave these elements last

Hydrogen and Oxygen

Limiting reactant

reactant that limits the chemical reaction; runs out first

Theoretical yield

max amount of product that can be made

What gives the theoretical yield

Limiting reactant

Percent yield formula

Actual/Theoretical X 100