Name: Katy Kim Date: April 19, 2021 Class Period 9.2
Molar Mass and Conversion Notes and Worksheet
Notes:
 An Isotopes is an atom that has the same number of protons as other atoms of the same element
do but that has a different number of neutrons (and a different atomic mass)
 Because isotopes have the same number of protons and electrons, they generally have similar
chemical properties.
 On the periodic table, the atomic mass displayed is an average of the atomic masses of all of that
elements isotopes.
 It is a calculated average so the mostly commonly found isotope have the most impact on the
mass.
 A mole is the SI base unit that describes the amount of a substance.
 Avogadono’s constant is the number of particles in 1 mole of a substance and is equal to
602213670000000000000000 or 6.02 x 1023.
 The Molar mass is the mass in grams of 1 mol of a substance.
 This is equal to the atomic mass of atoms measured in grams rather than amu’s.
 Example: The atomic mass of magnesium is equal to 24.30 amu. The molar mass of
magnesium is equal to 24.30 g.
Questions:
1) What is the mass of one mole of Br atoms?
- 80g
2) What is the mass of one mole of titanium atoms?
- 48g
3) What is the molar mass of tin?
- 119g/mol
4) What is the mass of one mole of chromium atoms?
- 52g
5) What is the mass of 6.02 x 1023 atoms of arsenic?
- 75g
6) How many atoms are there in one mole of atoms?
- 6.02 x 1023 atoms
7) What is the mass of one mole of Br2 atoms?
- 160g
8) What is the mass of one mole of water (H2O)?
- 18g
9) What is the molar mass of CaCl2?
- Mr: 110g/mol
10) What is the molar mass of K2Cr2O7?
- Mr: 294g/mol
Chemistry Worksheet: Calculations Based on Moles and Molar Mass
Substance
Molar Mass
(atomic mass in
grams)
75g/mol
Number of
Particles
(6.022 x 1023 x # of
moles)
Moles of Particles
(mass / molar mass)
OR (# of particles / 6.022
x 1023)
6.02x1023 x 3.5
= 2.107x1024
As
(Arsenic)
Mass (grams)
(molar mass x #
of moles)
M= 3.5 x 75
262.5grams of
arsenic atoms
3.5 moles of arsenic
atoms
46g/mol
6.02x1023 x3
= 1.806 x 1024
3 moles of formic acid
(138/46)
138 grams of
formic acid
HCOOH
(formic acid)
262g/mol
1.2 x 1024
molecules of
magnesium
phosphate
Mg3(PO4)2
(magnesium
phosphate)
64g/mol
1.806 x 1024
moles of sulfur
dioxide
SO2
(sulfur dioxide)
M = n x Mr
192grams of
sulfur dioxide
3.0 moles of sulfur
dioxide molecules
16g/mol
CH4
(methane)
2moles of magnesium 524grams of
phosphate
magnesium
(1.2 x1024/6.02 x 1023) phosphate
2.408 x 10 24
Moles of
methane
4 moles of methane
64 grams of
methane