There are terms used to equate a certain quantity of matter o For example 1 dozen = 12, 1 Ton = 2,000 LBs and 1 gross = 144. Before we get to the chemical terms lets convert between units we already know
For example – let’s say you want to buy some Bazooka Gum o You could buy it by the piece from the deli o You could buy it by the box from ShopRite o You could buy it by mass from the candy store
So, the different ways to measure Bazooka gum o 1 dozen = 12 pieces o 1 dozen = 1.75 boxes o 1 dozen = 168 grams
Based on those conversions, I can determine how much Bazooka gum I have, regardless of how it is measured. I have 95 pieces of Bazooka gum, how many grams do I have?
I have 95 pieces of Bazooka gum, how many grams to I have?
If I have 2 stadiums how many baseball bats do I want to purchase? 2 baseball players = 4 baseball bats 1 stadium = 18 baseball players 18 baseball players = 52 corn dogs
In chemistry, there are many way to measure the amount of substance o The count (quantity) o The volume (how much space it takes up) o The mass (the amount of matter) Knowing how the count, mass, and volume of an item relate to a common unit allows you to convert among these units.
In chemistry, we do not use a dozen. o Since atoms are so small, we need a quantity with a larger amount We use the mole (mol) o 1 mole = 6.022 X 10 23 representative particles (atoms, molecules, formula units) o It is known as Avogadro’s number
An Italian chemist whose important contributions was his resolution of the confusion surrounding atoms and molecules. Avogadro believed that particles could be composed of molecules and that molecules could be composed of still simpler units, atoms. The number of molecules in a mole (one gram molecular weight) was termed Avogadro's number
We usually are dealing with three types of representative particles o Molecules H 2 O and H 2 are molecules, covalently bonded o Atoms Al and Na are atoms, not bonded o Formula units CaCl 2 and NaOH are formula units, ionicly bonded
1 mole of any representative particle is always 6.02 X 10 23 Using this value we can convert between moles and atoms/ molecules/ formula units
For example: If a sample contains 0.476 mol of O 2, how many representative particles are present?
For example: If a sample contains 5.2 X 10 21 atoms of aluminum, how many moles are present?
We can determine the molar mass of representative particles o Molar mass is the mass of 1 mole of that substance The atomic mass is equal to the molar mass for an element o 1 mol Na = 22.99 g Na
For molecules and formula units, we must calculate the molar mass Let’s calculate the molar mass of SO 3 S = 1 X 32.07 = 32.07 O = 3 X 16.00 = 48.00 = 80.07 g/mol
We can use the molar mass of a substance to convert from moles to mass o Remember the molar mass is the mass of 1 mole of that substance o SO 3 = 80.07 g/mol = 80.07 g SO 3 1 mol SO 3
Using this relationship, we can easily convert a mole amount to a mass amount How many grams is there in a 0.750 mole sample of SO 3 ?
We can also convert a mass amount to a mole amount How many moles is there in a 28.5 gram sample of SO 3 ?