mass-mol_ mass-mass

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```					 Bellwork:
How is it possible for a jet airplane carrying
110 tons of jet fuel to emit 340 tons of carbon
dioxide?

The fuel is a hydrocarbon that is about to be combusted.
Combustion is a process in which oxygen combines with a
hydrocarbon to produce carbon dioxide and water. As the carbon-
based fuel combusts, each carbon is combined with two oxygen
atoms that come from the air, so the overall mass seems to increase
when compared to the starting amount of fuel. However, mass is
conserved, because the oxygen was part of the original reactants, it
just came from a different source.
 Bellwork:
The disinfectant hydrogen peroxide, H2O2, decomposes
to form water and oxygen gas. How many moles of O2
will result from the decomposition of 5.0 mol of
hydrogen peroxide?

2H2O2(l)          2H2O(l) + O2(g)
5.0 mol                       ? mol

1 mol O2
5.0 mol H2O2 x               = 2.5 mol O2
2 mol H2O2
 Bellwork:
Zinc metal can be obtained from zinc oxide, ZnO, by reacting
the oxide with the element carbon. The products of the
reaction are Zn and CO2. What mass in grams of zinc oxide is
needed to react completely with 5.00 mol of carbon?

2ZnO(s) + C(s)           2Zn(s) + CO2(g)
?g       5.00 mol

2 mol ZnO   81.39 g ZnO     814 g ZnO
5.00 mol C x             x             =
1 mol C   1 mol ZnO
Stoichiometry – Ch. 9

I.   Stoichiometric
Calculations

(p. 275-287)
OBJECTIVES
3.3.6 Calculate the amount in moles of a reactant or
product from the mass of a different reactant
or product.

3.3.7 Calculate the mass of a reactant or product
from the mass of a different reactant or product.
Conversions of Mass to
Amounts in Moles
Sample Problem 9-4
The first step in the industrial manufacture of nitric acid is the
catalytic oxidation of ammonia.

4NH3(g) + 5O2(g)               4NO(g) + 6H2O(g)
824 g                           ? mol
The reaction is run using 824 g of NH3 and excess oxygen.

a. How many moles of NO are formed

1 mol NH3     4 mol NO      48.4 mol NO
824 g NH3 x                x           =
17.04 g NH3   4 mol NH3
Sample Problem 9-4
The first step in the industrial manufacture of nitric acid is the
catalytic oxidation of ammonia.

4NH3(g) + 5O2(g)               4NO(g) + 6H2O(g)
824 g                                      ? mol

The reaction is run using 824 g of NH3 and excess oxygen.

b. How many moles of H2O are formed?

1 mol NH3     6 mol H2O     72.6 mol H2O
824 g NH3 x                x           =
17.04 g NH3   4 mol NH3
Chlorine gas can be produced commercially by passing an
electric current through a concentrated solution of sodium
chloride (brine).

2NaCl(g) + 2H2O(l)            2NaOH(aq) + Cl2(g) + H2(g)
250 g                                      ? mol

a. If the brine contains 250 g of NaCl, how many moles
of Cl2 can be produced?

1 mol NaCl      1 mol Cl2     2.14 mol Cl2
250 g NaCl x                x            =
58.44 g NaCl   2 mol NaCl
Chlorine gas can be produced commercially by passing an
electric current through a concentrated solution of sodium
chloride (brine).

2NaCl(g) + 2H2O(l)            2NaOH(aq) + Cl2(g) + H2(g)
250 g                                               ? mol

b. How many moles of H2 can be produced?

1 mol NaCl      1 mol H2      2.14 mol Cl2
250 g NaCl x                x            =
58.44 g NaCl   2 mol NaCl
Mass-Mass Calculations
Sample Problem 9-5
Tin(II) fluoride, SnF2, is used in some toothpastes. It is made by
the reaction of tin with hydrogen fluoride according to the
following equation.

Sn(s) + 2HF(g)             SnF2(s) + H2(g)
30.00 g            ?g
How many grams of SnF2 are produced from the reaction of
30.00 g of HF with Sn?

1 mol HF     1 mol SnF2   156.71 g SnF2 =   117.5 g SnF2
30.00 g HF x              x            x
20.01 g HF   2 mol HF     1 mol SnF2
Sodium peroxide reacts vigorously with water to produce
sodium hydroxide and oxygen.

2Na2O2(s) + 2H2O(g)               4NaOH(s) + O2(g)
50.0 g                                         ?g

a. What mass in grams of O2 is produced when 50.0 g of
Na2O2 react?

1 mol Na2O2     1 mol O2   32.00 g O2   = 10.3 g O2
50.0 g Na2O2 x                x           x
77.98 g Na2O2 2 mol Na2O2 1 mol O2
Sodium peroxide reacts vigorously with water to produce
sodium hydroxide and oxygen.

2Na2O2(s) + 2H2O(g)              4NaOH(s) + O2(g)
50.0 g          ?g

b. What mass in grams of water is needed to react
completely with the Na2O2?

1 mol Na2O2    2 mol H2O   18.02 g H2O =   11.5 g H2O
50.0 g Na2O2 x                x           x
77.98 g Na2O2 2 mol Na2O2 1 mol H2O
Homework
HW 9-1,2
pg. 285 Practice #1-2
pg. 287 Practice #1-3
Due: Friday 1/11

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