Information given by chemical equations

1
Information given by chemical equations
2 C6H6 (l) 15 O2 (g) ? 12 CO2 (g) 6 H2O
(g)

• In this equation there are 2 molecules of benzene
  reacting with 15 molecules of oxygen to produce
  12 molecules of carbon dioxide and 6 molecules of
  water.

• This equation could also be read as 2 moles of
  benzene reacts with 15 moles of oxygen to produce
  12 moles of carbon dioxide and 6 moles of water.

Since the relationship between the actual number
of molecules and the number of moles present is
6.02 x 1023, a common factor between all species
involved in the equation, a MOLE RATIO
relationship can be discussed.
2
Information given by chemical equations
2 C6H6 (l) 15 O2 (g) ? 12 CO2 (g) 6 H2O
(g)
The MOLE RATIO for benzene and oxygen is 2 15.
It can be written as 2 moles C6H6
or as 15 moles of O2 15 moles O2
2 moles
of C6H6
The MOLE RATIO for oxygen and carbon dioxide is
15 12. It can be written as 12 moles CO2
or as 15 moles of O2 15
moles O2
12 moles of CO2

• NOTE The MOLE RATIO is used for converting
  moles of one substance into moles of another
  substance. Without the balanced equation there
  is no other relationship between two different
  compounds.

3
Using the mole ratio to relate the moles of one
compound to the moles of another compound is the
part of chemistry called STOICHIOMETRY !!!!!
2 H2 (g) O2 (g) ? 2 H2O (g)
Q. How many mole of hydrogen are necessary to
react with 2 moles of oxygen in order to produce
exactly 4 moles of water?
A. 2 mol O2 (2 moles H2 / 1 mole O2) 4 mole
H2
4
STOICHIOMETRY
The Stoichiometry Flow Chart
Use mole ratio from equation
Use Molar mass (A)
Use Molar mass (B)
5
STOICHIOMETRY
2 H2 (g) O2 (g) ? 2 H2O (g)
Q1. How many moles of hydrogen are necessary to
react with 15.0 g of oxygen?
A. 15.0g O2 (1 mole O2 ) ( 2 mole H2) 0.938
moles H2 32.0 g 1 mole O2
Q2. How many grams of hydrogen are necessary to
react with 15.0 g of oxygen?
A. 15.0g O2 (1 mole O2 ) ( 2 mole H2) ( 2.016 g
H2) 1.89 g H2 32.0 g 1 mole O2
1 mole H2
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STOICHIOMETRY
2 H2 (g) O2 (g) ? 2 H2O (g)
Q3. How many grams of water are produced from
15.0 g of oxygen?
A. 15.0g O2 (1 mole O2 ) ( 2 mole H2O) ( 18.0 g
H2O) 16.9 g H2O 32.0 g 1 mole
O2 1 mole H2O
Q4. How much hydrogen and oxygen is needed to
produce 25.0 grams of water?
A. 25.0g H2O (1 mole H2O ) ( 2 mole H2) ( 2.016 g
H2) 2.80 g H2 18.0 g 2
mole H2O 1 mole H2
A. 25.0g H2O (1 mole H2O ) ( 1 mole O2) ( 32.0 g
O2) 22.2 g O2 18.0 g 2
mole H2O 1 mole O2 Notice that the Law of
Conservation of Mass still applies.
7
How many grams of solid are formed when 10.0 g of
lead reacts with excess phosphoric acid?

1. Write the chemical equation Pb H3PO4 ? ?

You recognize that this is a single displacement
(replacement) reaction. So Pb (a metal) will
displace (replace) H (the cation). Pb H3PO4 ?
Pb3(PO4)2 H2
2. Balance the equation 3 Pb2 H3PO4 ?
Pb3(PO4)2 3 H2
3. Make a list under the appropriate substance 3
Pb2 H3PO4 ? Pb3(PO4)2 (s) 3 H2 (g)
10.0g m?
Start with what is given 10.0gPb (1 mole Pb)( 1
mole Pb3(PO4)2)(811 g Pb3(PO4)2) 13.1 g
Pb3(PO4)2 207 g Pb 3 mole Pb
1 mole Pb3(PO4)2
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PRACTICE PROBLEM 18

• 1. How many grams of gas can be produced from
  0.8876 moles of HgO?
• 2 HgO ? 2 Hg O2
• 2. How many moles of fluorine are required to
  produce 12.0 grams of KrF6? Given the equation
  Kr 3 F2 ? KrF6
• 3. How many grams of Na2CO3 will be produced
  from the thermal decomposition of 250.0 g of
  NaHCO3?
• 4. How many grams of CO2 can be produced by
  the reaction of 75.0 grams of C2H2 with excess
  oxygen?
• 5. Cu 2 AgNO3 ? Cu(NO3)2 2 Ag.
• How many grams of silver is produced when 125.0 g
  of copper is reacted with excess silver nitrate
  solution?

14.20g
0.182 mol
157.7 g
254 g
424.9 g
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GROUP STUDY PROBLEM 18

• ______1. How many grams of liquid product can
  be produced from 3.55 moles of HgO?
• 2 HgO ? 2 Hg O2
• ______2. How many moles of fluorine are
  required to produce 3.0 grams of KrF6? Given the
  equation Kr 3 F2 ? KrF6
• ______3. How many grams of Na2CO3 will be
  produced from the decomposition of 20.0g of
  NaHCO3?
• ______4. How many grams of O2 are needed to
  combust 55.0 grams of C2H4?
• ______5. Cu 2 AgNO3 ? Cu(NO3)2 2 Ag.
• How many grams of silver is produced when 50.0 g
  of copper is reacted with excess silver nitrate
  solution?