Chapter 6 Chemical Composition

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

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

6.3 The Mole Mole- the number equal to the number of carbon atoms in 12.01 grams of carbon Avogadro’s number- 6.022x1023 units A mole in context is similar to describing something in dozens.

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

6.5 % 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%

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

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