Ch. 10
Stoichiometry
GCC
CHM 130
10.1 Interpreting a Chemical Equation
2 NO (g)
2 molecules
10 molecules
2 moles
N2 (g)
+
+
O2 (g) → 2 NO2 (g)
1 molecule
5 molecules
1 mole
3 H2 (g) →
___ molecule(s) ___ molecule(s)
____ mole
____ mole
2 molecules
10 molecules
2 mole2
2 NH3 (g)
___molecule(s)
____ mole
So coefficients give us molecule
or mole ratios.
10.2 Mole-Mole Ratios
___ Fe2O3 (s) + ___ CO (g) g __ Fe (s) + ___CO2 (g)
1 mol
3 mol
Examples: 1 mol Fe2O3
3 mol CO
2 mol
3 mol CO
1 mol Fe2O3
3 mol
2 mol Fe
3 mol CO
1. How many moles of iron can be formed from
10.2 moles of carbon monoxide?
10.2 mol CO ( 2 mol Fe / 3 mole CO) = 6.80 mol Fe
2. How many moles of iron(III) oxide are
needed to form 17 moles of carbon dioxide?
17 mol CO2 ( 1 mol Fe2O3 / 3 mole CO2) = 5.7 mol Fe2O3
Another Example
Balance this reaction:
2 SO2 (g) + ___O2(g) g ___SO
2
___
3(g)
How many moles of SO3 will form if 0.165
moles of oxygen gas react?
0.165 mol O2 (2 mol SO3 / 1 mol O2) = 0.330 mol SO3
How many moles of SO2 are needed to
make 0.042 moles of sulfur trioxide?
0.042 mol SO3 (2 mol SO2 / 2 mol SO3) = 0.042 mol SO2
10.3-4 Mass – Mass Stoichiometry
Grams
given
Molar
Mass
3 FeO(s)
Moles
given
Mole
Ratio
Moles
find
+ 2 Al(s) g 3 Fe(s)
Molar
Mass
+
Grams
find
Al2O3(s)
1. Calculate the mass of iron (II) oxide needed to react completely
with 5.55 g of aluminum.
2. Calculate the mass of aluminum oxide produced when 10.25 g of
aluminum reacts completely.
3 FeO(s)
+ 2 Al(s) g 3 Fe(s)
 mol Al
1. 5.55 g Al 
 26.98 g Al
+
Al2O3(s)
  3 mol FeO   71.85 g FeO 

 
 
2 mol Al   mol FeO 


= 22.2 g FeO
 mol Al
2. 10.25 g Al 
 26.98 g Al
= 19.37 g Al2O3
  1 mol Al 2 O 3   101.96 g Al 2 O 3 


 
 mol Al 2 O 3 
2
mol
Al



10.5-6 Mass – Volume and
Volume-Volume problems
Write and balance the reaction of HCl
(aq) and solid cobalt. Note cobalt will
be +2 as an ion in this example.
2 HCl(aq) + Co(s) g CoCl2(aq) + H2(g)
How many liters of gas at STP will form if
5.00 grams of cobalt reacts?
5.00 g Co(mol/58.93)(1 molH2/1molCo)(22.4L/mol)
= 1.90 L H2
If 2.374 L of hydrogen gas formed, how many
grams of HCl reacted?
2.374 L H2 (mol/22.4L)(2 mol HCl/1 mol H2)(36.46 g/mol)
= 7.73 g HCl
HCl gas plus oxygen gas produces
chlorine gas and water vapor.
• How many liters of chlorine can be formed if 3.00 liters of
oxygen react completely at STP?
4 HCl(g) + O2(g) g 2 Cl2(g) + 2 H2O(g)
3.00 L O2 (mol / 22.4 L)(2 mol Cl2 / 1 mol O2)(22.4 L/mol)
= 6.00 L Cl2
Skip sections 10.7 - 9
Try at Home
Carbon reacts with oxygen gas to form carbon
monoxide. How many liters of carbon
monoxide at STP can be made from
1. 15.0 grams carbon?
2. 20.0 liters of oxygen gas?
Remind me to show answers next time
2 C(s) + O2(g) g 2 CO(g)
15.0 g C (mol /12.01g)(2 mol CO/2 mol C)(22.4 L / mol)= 28.0 L CO
20.0 L O2 (mol /22.4L)(2 mol CO /1 mol O2)(22.4 L/mol)= 40.0 L CO
Self Test
• Page 288
• Try 1-6, 10, 14
• Answers in Appendix J