Unit 7 (Chapter 8) Flashcards
Avogadro’s Number
6.022*10^23
empirical formula
formula based on observation or experiment \
formula mass (molecular mass)
- mass of one molecule or formula unit
- in other words, the mass of one particle of a compound (a substance represented by a formula)
- written in amu(s)
- need formula and periodic table
- sum of individual atomic masses
- associated with ionic and molecular compounds
- value found by adding
molar mass
mass of a mole (the mass from the periodic table in grams instead of amus)
molar volume
the volume of a mole
molecular formula
tells us the actual number of elements present in a formula
percent composition
the percent of the total mass of the compound that is due to that element
Avogadro’s Law
if you have two gases at the same temperature and pressure, they will occupy the same volume only if they contain the same number of molecules
Atomic mass
- the mass of an atom (NOT the same as mass number)
- value found on periodic table
- associated only with elements
molecular compound
molecule
ionic compound
formula unit
formula unit
- particle of ionic compound
- associated only with ionic compounds
Mole city and particle-ville
1 mol = 6.022*10^23 atoms; molecules; formula units
Mole city and mass town
1 mol = grams from periodic table (g)
Mole city and gas volume corners
1 mol = 22.4L at STP
Atomic mass unit
- label that goes at end of number
- associated with elements, ionic compounds, molecular compounds
Empirical formula steps
- start with mass values or percent composition values
- find masses if not already masses
- convert g to mol (use molar mass)
- divide by smallest mol
Empirical formula tips
If mol/smallest mol = .5, multiply each by 2
If mol/smallest mol = .33333 multiply each by 3
If mol/smallest mol = .25, multiply each by 4
Empirical formula must be reduced ratio
do not limit sig figs until final step
Molecular formula formula
actual molar mass (given in problem) /
empirical molar mass (added from empirical formula)
