1. Chapter 6
Chemical Composition

2. 6.1Counting by Weighing Average mass= total mass/ number of objects
This can be used in labs by taking the average result of your trials

3. 6.2 Atomic Mass: Counting Atoms by Weighing
Atomic mass units= amu
1 amu= 1.66x10-24 g
Amu is a measurement of mass
One atom is equivalent to the mass of an element on the periodic table

4. 6.3 The Mole
Mole- the number equal to the number of carbon atoms in grams of carbon
Avogadro’s number x1023 units
A mole in context is similar to describing something in dozens.

5. 6.4 Molar Mass
Molar mass of a substance is the mass(in grams) of 1 mole of that substance
Molar mass can be found by adding up the masses of the atoms in the compound

6. 6.5 % Composition of Compounds
% composition can be found by:
Mass of element(s) present in 1 mol of the compound/1 mol of compound
All percents should add up to 100%

7. 6.7 Calculation of Empirical Formulas
Find how many moles of each element are present in the compound
Divide each elements mol number by the lowest mol number
Multiply the numbers from the previous step to make sure all numbers are whole numbers
Empirical formula is the smallest form of the compound

8. 6. 8Calculation of Molecular Formulas
Calculate the empirical formula
Find the molar mass
Molar mass/ empirical formula mass
Round to a whole by multiplying
Multiply each element in the empirical formula to find the molecular formula