chapter 3 section 4 notes using moles to count atoms
TRANSCRIPT
Chapter 3 Section 4 Notes
Using Moles to Count Atoms
What is a mole?
The SI base unit that describes the amount of a substance; a collection of a very large number of particles.
What is a mole useful for?
Counting small particles
Avogadro’s Constant
Avogadro’s Constant: the number of particles in 1 molEquals 6.022 x 1023 particles/ mol 602,213,670,000,000,000,000,000 particles
How does Avogadro’s constant relate to a mole of something? It is the number of particles in one mole of
anything.
Moles and Grams are related
Molar Mass: the mass in grams of 1 mol of a substance
How do you find molar mass?The average atomic mass is equal to molar
mass. Simply look on the Periodic Table!
Practice
Determine the molar mass of the following elements: (Round to the nearest hundredth) Manganese, Mn
54.94 g/mol Cadmium, Cd
112.41 g/mol Arsenic, As
74.92 g/mol Strontium, Sr
87.62 g/mol
More Practice
Determine the mass, in grams of each of the following:0.48 mol of platinum
2.50 mol of sulfur
0.48 mol x 1 mol
195.08 g = 94 g
2.50 mol x1 mol32.07 g = 80.2 g
Even More Practice
Determine how many moles are present in each of the following:620 g of mercury
11 g of silicon
620 g x
200.59 g
1 mol = 3.09 mol
11 g x28.09 g1 mol = 0.39 mol
Compounds also have molar mass
To find the molar mass of a compound, add up the molar masses of all the atoms in a molecule of the compound.
Example: H2OMolar Mass of Hydrogen: 1.01 x 2 = 2.02 g/mol
Molar Mass of Oxygen: 16 g/mol Total Mass of H2O: 2.02 g + 16 g = 18.02 g/mol