Example of how to solve a mass-to-mass stoichiometry problem
Example Problem: If 1.00 gram of the simple sugar fructose (C6H12O6)
is burned in atmospheric oxygen of (O2), what mass of carbon dioxide
(CO2) would be produced according to the equation below?
C6H12O6(s) + 6O2(g)
6CO2(g) + 6H2O(l)
Step 1: Interpret the problem and determine what the starting species is.
Put the starting species amount, measurement unit, and species formula
in a fraction over 1.
1.00 g C6 H12 O6
Ex:
1
Step 2: Calculate the molar mass of the starting species in the manner
required in this class. The molar mass calculation MUST include an
equality statement at the end.
Ex:
C: 12.0107 ×
6
=
H: 1.00794 ×
O: 15.9994 ×
12
6
=
=
72.0642
12.09528
95.9964
180.15588 g C6H12O6 = 1 mol C6H12O6
180.1559 g C6H12O6 = 1 mol C6H12O6
Step 3: Use the equality statement from step 2 to write a conversion unit.
Put the side of the equality statement that matches the units and species
of the starting amount on the bottom. Cancel units and species.
Multiply/divide/round.
1.00 g C6 H12 O6
1 mol C6 H12 O6
Ex:
1
180.1559 g C6 H12 O6
0.00553232 mol C6 H12 O6
0.00553 mol C6 H12 O6
.
Your mass-to-mass stoichiometry worksheet
Your problem #1: If 2.25 grams of carbon disulfide (CS2) is reacted with
an excess amount of fluorine gas (F2), what mass of sulfur (S8) would be
produced according to the equation below?
4CS2(s) + 4F2(g)
4CF2(s) + S8(s)
Example of how to solve a mass-to-mass stoichiometry problem
(continued)
Step 4: Use the answer from step 3 as the new starting amount; put it
over 1. Use the coefficients from the balanced chemical equation to
write a molar ratio. The molar amount on the bottom of that ratio
MUST match the starting amount. The molar amount of the species
being sought must be on the top. Cancel units and species.
Multiply/divide/round.
0.00553 mol C6 H12 O6
6 mol CO2
1
Ex:
1 mol C6 H12 O6
0.03318 mol CO2
0.0332 mol CO2
.
Step 5: Use the answer from step 4 as the new starting amount; put it
over 1. Calculate the molar mass of the starting species in the manner
required in this class. Use the equality statement from the molar mass
calculation to write a conversion unit. Cancel units and species.
Multiply/divide/round.
0.0332 mol CO2 44.0095 g CO2
Ex:
1
1 mol CO2
1.4611154 g CO2
Ex:
C: 12.0107
O: 15.9994
×
×
1.46 g CO2
1
2
=
=
12.0107
31.9988
44.0095
.
g CO2 = 1 mol CO2
Your mass-to-mass stoichiometry worksheet
(continued)
Conversion Worksheet 01
Moles of one species to moles of another species conversions
Step 1: Starting amount goes over 1.
Units of measurement and species must be included.
Multiplication sign follows that.
Step 2: No equality is needed but a balanced equation is required.
Step 3: Build a molar ratio from the coefficients and species in the balanced equation.
The coefficients in front of each species in the equation are treated as moles of that species in the molar ratio.
The side of the equality statement with units and species that match the starting amount goes on the bottom of the conversion unit.
The other side of the equality statement goes on the top of the conversion unit.
Step 4: Cancel units and species and solve the problem.
Round the answer if needed.
Moles of species 1 to moles of species 2 conversion problems:
1.
Using the following balanced chemical equation, how many moles of water (H 2O) will be produced from 4.00 moles of butane (C4H10) and an
excess of atmospheric oxygen (O2)?
2C4H10(l) + 13O2(g) 8CO2(g) + 10H2O(g)
Show ALL your work here.
2.
Using the following balanced chemical equation, how many moles of hydrogen gas (H 2) will be produced from 2.25 moles of hydrochloric acid
(HCl) and an excess of magnesium metal (Mg)?
Mg(s) + 2HCl(aq)
MgCl2(aq) + H2(g)
Show ALL your work here.
Conversion Worksheet 02
Mole to mass and mass to mole conversions
Step 1: Starting amount goes over 1. Units of measurement and species must be included. Multiplication sign follows that.
Step 2: Calculate the molar mass of the starting species. The molar mass is the sum of all the atomic masses of all the atoms in a formula. An example of
the required format for calculating molar mass in this class is shown below. The example is for silver chloride:
Ag: 107.8682 × 1 = 107.8682
Cl: 35. 453
× 1 =
35. 453
143.3212
→ 143.321 g AgCl = 1 mol AgCl
Note the equality statement at the end of the molar mass calculation.
Step 3: Build a conversion unit from the equality statement. The side of the equality statement with units and species that match the starting amount goes
on the bottom of the conversion unit. The other side of the equality statement goes on the top of the conversion unit.
Step 4: Cancel units and species and solve the problem. Round the answer if needed.
Mole to mass conversion problems:
3.
What is the mass of 9.99 moles of nickel sulfide (NiS)?
Show ALL your work here.
Mass to mole conversion problems:
4.
How many moles of mercury(II) sulfide (HgS) are there in 2.25 g of mercury(II) sulfide?
Show ALL your work here.
Conversion Worksheet 03
Mole to particle and particle to mole conversions
Step 1: Starting amount goes over 1. Units of measurement and species must be included. Multiplication sign follows that.
Step 2: Write equality statement based on the fact that 1 mole of any particles (including atoms, molecules, ions, and formulas) equals 6.02 × 1023 of those
particles.
6.02 × 1023 x = 1 mol x.
Step 3: Build a conversion unit from the equality statement. The side of the equality statement with units and species that match the starting amount goes
on the bottom of the conversion unit. The other side of the equality statement goes on the top of the conversion unit.
Step 4: Cancel units and species and solve the problem. Round the answer if needed.
Mole to particle conversion problems:
5.
How many atoms are there in 15.00 moles of xenon (Xe)?
Show ALL your work here.
Particle to mole conversion problems:
6.
How many moles are there in 1.22 × 1025 molecules of hydrogen cyanide (HCN) ?
Show ALL your work here.