Name:
Daily: Molar Mass
Date:
Period:
Interpreting formulas:
A chemical formula tells two things 1) the elements present and 2) the relative number of
atoms of each element. For example, water (H2O) is composed of two atoms of hydrogen
to one* atom of oxygen. Occasionally, the formula is a little more complicated. For
example, magnesium phosphate has the formula, Mg3(PO4)2. The two outside of the
parenthesis is distributed to all the atoms inside the parenthesis; just like math class!
Therefore, there are three atoms of magnesium, two atoms of phosphorous, and eight
atoms of oxygen!
*note chemists do not write the, 1, in a chemical formula.
Complete the following by writing the number of atoms of each element present in the
blank.
a. C6H12O6
_____Carbon
_____Hydrogen ______Oxygen
b. MgBr2
_____Magnesium _____Bromine
c. O2
_____Oxygen
d. Mg(OH)2
_____Magnesium _____Oxygen
_____Hydrogen
e. Na3PO4
_____Sodium
_____Phosphorous _____Oxygen
f. (NH4)2SO4
___Nitrogen ____Hydrogen
____Sulfur ____Oxygen
Formula Mass- equals the sum of the atomic masses of all of the atoms represented by a
formula of the substance, measured in atomic mass units.
Formula Mass: Calculate the formula mass.
a. C6H12O6
b. MgBr2
c. O2
d. Mg(OH)2
e. Na3PO4
f. (NH4)2SO4
Molar Mass- The mass, in grams, of one mole of the compound. Molar mass is also
referred to as molecular weight.
Molar Mass: write the molar mass of the following.
a. C6H12O6______________
b. MgBr2___________
c. O2_____________
d. Mg(OH)2____________
e. Na3PO4___________
f. (NH4)2SO4___________
g. Cu_________
h. Al_________
I. Mg_________
Mole- the SI unit for amount of substance; it is abbreviated mol. The mole is equal to
6.022 x 1023 atoms/molecules and is equal to, in grams, the molar mass of a substance. The
number 6.022 x 1023 is known as Avogadro’s number (N). At standard temperature and
pressure, 1 atmosphere / 273.15 kelvin, a mole of gas is equal to 22.4 dm3. The mole is
abbreviated, mol.
The Mole:
Is the mole small or large? Why?
1. A dozen pencils equals ________ pencils.
a. A foot equals ________inches.
b. An hour equals ________minutes.
c. A pair of socks _______socks.
d. A mole equals __________ atoms.
e. A mole equals ___________liters.
2. Two dozen cookies equals _________cookies.
a. Three hours equals _______minutes.
b. Two moles ____________atoms.
c. Three moles____________ molecules.
Stoichiometry- The study of quantitative relationships that can be derived from chemical
formulas and equations.
Moles to Atoms
2.1 moles of Na
=_______________atoms Na
Atoms of Moles
4.0 x 1024 atoms of Al
=_____________molAl
4.8 moles of Be
=______________atoms Be
2.1 x 1023 atoms of Cu =
__________molCu
9.0 moles of Rb = ___________moles
Rb
8.1 x 1024 atoms of K =
___________molK
5.2 moles of W =
_______________atoms W
8.4 x 1024 atoms of Cr
=____________molCr
Moles to Volume
Volume to Mole
1 mole of Kr = ___________LK
44.8 L of Xe = __________mol Xe
7.2 moles of He =____________LHe
18 L of H =__________mol H
4.8 moles of Ar = ___________LAr
105 L of Br2 =__________mol Br2
8.2 mole Ne = __________LNe
18 L of O2 = ________mol O2
Moles to Mass
3.7 moles of Fe =____________g Fe
Mass to Moles
52.90 g of Si
=__________________mol Si
8.2 moles of Ni = ___________g Ni
73.2 g of As = ___________mol As
8.2 moles C =_____________g C
82.0 g of Mg = ________________mol
Ca.
3 moles of Al =_____________g Al
Mass to Atoms
25.45 g of S = _________atoms of S
105 g of Au = _________atoms of Au
18 g of Ag =__________ atoms of Ag
109 g of Hg = __________atoms of Hg
54.3 g of N =_______________mol N
Atoms to Mass
4.2 x 1023 atoms of Pb = ___________ g of Pb
8.2 x 1024 atoms of Zn = ___________g of Zn
1.8 x 1023 atoms of P = ___________g of P
4.5 x 1023 atoms of B = __________g of B
Mixed Problems
1. 18 grams of cobalt = _________atoms Co
2. 9 mol of barium = ___________ g of Ba
3. 6.0 x 1021 atoms of magnesium = ________g Mg
4. 9.02 x 1023 atoms of lead =___________mol Pb
5. 25.3 g of lithium =_________mol Li
6. 18 mol of mercury = _________atoms of Hg
7. 24.3 L of Neon = _________moles of Neon
Even more practice!!!
1. Juglone, a dye used for centuries, is produced from the husks of black walnuts.
Juglone has the formula, C10H6O3. Calculate the molecular mass of Juglone.
B. If you have 500 grams of the dye, how many molecules are present?
2. Calcium carbonate (CaCO3) is the principal compound found in chalk. Calculate
the molar mass of calcium carbonate.
B. If you have 2 moles of calcium carbonate, what is the mass of the sample?
3. Ascorbic acid (vitamin C) is an essential vitamin. What is the molar mass of
ascorbic acid (C6H8O6)?
B. If you have 6.07 x 1024 molecules, what is the mass of the ascorbic acid sample?
4. What is the molar mass of aspirin (C9H8O4)?
B. If you have 100 grams of aspirin, how many moles are present?
5. Calculate the molar mass of water (H2O).
B. If you have 12.7 L of water vapor, how many molecules are present?
6. Calculate the molar mass for potassium permanganate (KMnO4).
B. If you have 1.2 moles of potassium permanganate, what is the mass of your sample?