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Science, Technology, and Society
Methyl Alcohol: Fuel with a Future?
S
outhern California is famous
takes about twice as many gallons of
for many things, and among
methanol as gasoline to travel a
them, unfortunately, is smog.
given distance, a methanol-powered
Smog is produced when pollucar’s fuel tank must be twice the
tants in the air are trapped near
usual size. However, although costs
the ground and are caused to revary greatly depending on market
act by sunlight. A step being Image not available for this conditions, the cost of methanol avconsidered by the state of Cali- CD-ROM. Please refer to
erages about half that of gasoline, so
fornia to help solve the smog
the net cost is about the same for
the image in the textbook.
problem is to replace gasoline
both fuels.
with methyl alcohol (usually
A second disadvantage of
called methanol). One advanmethanol is that its high affinity for
tage of methanol is that it reacts
water causes condensation from the
more nearly completely than
air, which leads to increased corrogasoline with oxygen in a car’s
sion of the fuel tank and fuel lines.
engine, thus releasing lower
This problem can be solved by using
amounts of unburned fuel into A crewman adds methanol fuel to
more expensive stainless steel for
the atmosphere. Methanol also a race car in the lndianapolis 500
these parts.
produces less carbon monoxide during a pit stop.
The most serious problem with
(CO) in the exhaust than does
methanol may be its tendency to form
gasoline. Carbon monoxide not
formaldehyde, HCHO, when it is comonly is toxic itself but also encourages the formabusted. Formaldehyde has been implicated as a cartion of nitrogen dioxide by the reaction
cinogen (a substance that causes cancer). Formaldehyde can also lead to ozone formation in the
CO(g) O2(g) NO(g) n CO2(g) NO2(g)
air, which causes even more severe smog. Researchers
Nitrogen dioxide is a reddish-brown gas that leads
are now working on catalytic converters for exhaust
to ozone formation and acid rain.
systems to help decompose the formaldehyde.
Using methanol as a fuel is not a new idea. For
To test the feasibility of methanol as a motor fuel,
example, it is the only fuel allowed in the openCalifornia has operated several hundred vehicles on
wheeled race cars used in the Indianapolis 500 and
methanol since 1980. Because accessibility to
in similar races. Methanol works very well in racing
methanol is limited, cars are now being prepared
engines because it has outstanding antiknock charthat can run on methanol or gasoline. These vehiacteristics, even at the tremendous speeds at which
cles are being tested on a large scale in California.
these engines operate.
So if you live in southern California, in a few years
The news about methanol is not all good, howyour neighborhood “gas station” may actually be
ever. One problem is lower fuel mileage. Because it
pumping methanol.
Mass Calculations: Comparing Two Reactions
Objective: To compare the stoichiometry of two reactions.
I
n this section we will consider the relative effectiveness of two antacids to
illustrate how chemical calculations can be important in daily life.
Baking soda, NaHCO3, is often used as an antacid. It neutralizes excess
hydrochloric acid secreted by the stomach. The balanced equation for the reaction is
NaHCO3(s) HCl(aq) n NaCl(aq) H2O(l) CO2(g)
9.5 Mass Calculations: Comparing Two Reactions
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Two antacid tablets containing HCO3
dissolve to produce CO2 gas.
Milk of magnesia, which is an aqueous suspension of magnesium hydroxide, Mg(OH)2, is also used as an antacid. The balanced equation
for its reaction is
Mg(OH)2(s) 2HCl(aq) n 2H2O(l) MgCl2(aq)
Which antacid can consume the most stomach acid, 1.00 g of
NaHCO3 or 1.00 g of Mg(OH)2?
Before we begin, let’s think about the problem to be solved.
The question we must ask for each antacid is, How many moles of
HCl will react with 1.00 g of each antacid? The antacid that reacts
with the larger number of moles of HCl is more effective because
it will neutralize more moles of acid. A schematic for this procedure is
Antacid
HCl
n
Products
1.00 g
antacid
Use molar mass
of antacid
Moles of
antacid
Use mole ratio from
balanced equation
Moles
of
HCl
Notice that in this case we do not need to calculate how many grams of HCl
react; we can answer the question with moles of HCl. We will now solve this
problem for each antacid. Both of the equations are balanced, so we can proceed with the calculations.
Using the molar mass of NaHCO3, which is 22.99 g 1.008 g 12.01 g 3(16.00 g) 84.01 g, we determine the moles of NaHCO3 in 1.00
g of NaHCO3.
1 mol NaHCO3
1.00 g NaHCO3 0.0119 mol NaHCO3
84.01 g NaHCO3
1.19 102 mol NaHCO3
1 mol HCl
Next we determine the moles of HCl, using the mole ratio .
1 mol NaHCO3
1 mol HCl
1.19 102 mol NaHCO3 1.19 102 mol HCl
1 mol NaHCO3
Thus 1.00 g of NaHCO3 neutralizes 1.19 102 mol of HCl. We need to compare this to the number of moles of HCl that 1.00 g of Mg(OH)2 neutralizes.
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Using the molar mass of Mg(OH)2, which is 24.31 g 2(16.00 g) 2(1.008 g) 58.33 g, we determine the moles of Mg(OH)2 in 1.00 g of
Mg(OH)2.
1 mol Mg(OH)2
1.00 g Mg(OH)2 0.0171 mol Mg(OH)2
58.33 g Mg(OH)2
1.71 102 mol Mg(OH)2
To determine the moles of HCl that react with this amount of Mg(OH)2, we
2 mol HCl
use the mole ratio .
1 mol Mg(OH)2
2 mol HCl
1.71 102 mol Mg(OH)2 3.42 102 mol HCl
1 mol Mg(OH)2
Therefore, 1.00 g of Mg(OH)2 neutralizes 3.42 102 mol of HCl. We have
already calculated that 1.00 g of NaHCO3 neutralizes only 1.19 102 mol
of HCl. Therefore, Mg(OH)2 is a more effective antacid than NaHCO3 on a
mass basis.
Self-Check Exercise 9.6
In this section we have answered one of the questions we posed in the introduction to this chapter. Now let’s see if you can answer the other question posed there. Determine what mass of carbon monoxide and what mass
of hydrogen are required to form 6.0 kg of methanol by the reaction
CO(g) 2H2(g) n CH3OH(l)
Lithium (Li)
F
or the first 150 years after its discovery in 1817,
lithium was a rather humble element. It seemed
to have very few uses. In the last 30 years, however,
lithium has been found to be a powerful psychoactive drug.
The psychological effects of lithium were discovered in the 1940s by accident by an Australian psychiatrist named John Cade. Cade was studying patients with manic-depressive syndrome, a disease
that causes its victims to experience extreme feelings ranging from high mania to deep depression.
Cade thought the disease might be due to problems in metabolizing uric acid. Consequently, he administered lithium salts of uric acid along with
lithium carbonate to animals. The result was a dra-
matic calming effect. Cade noticed similar effects
when he tried these treatments on himself and on
a few patients with manic-depressive disease. It was
not until a decade later that a Danish doctor, Mogens Schou, discovered that lithium—not the uric
acid—caused the dramatic effects.
In the last 50 years, lithium has become the most
popular drug for treating manic depression. Despite
the fact that it has helped millions of people, we
are still not sure how this element controls mania
and relieves depression. Lithium appears to help
regulate the levels of certain chemicals that transmit messages in the brain. Studies continue to explore how this once underrated element alters extreme moods so profoundly.
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