In a Reuters news report dated February 3,2010,President Obama is quoted as saying,"By 2022 we will more than double the amount of biofuels we produce to 36 billion gallons,which will decrease our dependence on foreign oil by hundreds of millions of barrels per year." Use the following information to determine the fraction of our projected 2022 total energy demand this target represents to assess its significance.(M = mega = 10⁶) U.S.projected annual energy demand in 2022: equivalent of 22 $\times$ 10³ Mbarrels of oil
Energy density of oil: 5.9 $\times$ 10³ MJ/barrel
Energy density of biofuels: 1.0 $\times$ 10² MJ/gal
Mass density of petroleum: 9.0 $\times$ 10² g/L
Mass density of biofuels: 8.0 $\times$ 10² g/L
1 gal = 3.785 L

Question

In a Reuters news report dated February 3,2010,President Obama is quoted as saying,"By 2022 we will more than double the amount of biofuels we produce to 36 billion gallons,which will decrease our dependence on foreign oil by hundreds of millions of barrels per year." Use the following information to determine the fraction of our projected 2022 total energy demand this target represents to assess its significance.(M = mega = 10⁶) U.S.projected annual energy demand in 2022: equivalent of 22

\times

10³ Mbarrels of oil
Energy density of oil: 5.9

\times

10³ MJ/barrel
Energy density of biofuels: 1.0

\times

10² MJ/gal
Mass density of petroleum: 9.0

\times

10² g/L
Mass density of biofuels: 8.0

\times

10² g/L
1 gal = 3.785 L

Quizplus · Accepted Answer

First, we need to calculate the total energy demand in 2022 in MJ (megajoules). We do this by multiplying the projected annual energy demand in 2022 (converted to barrels of oil) by the energy density of oil:
22 x 10^13 barrels/year x 5.9 x 10^6 MJ/barrel = 129.8 x 10^21 MJ/year

Next, we need to calculate the total energy that will come from biofuels in 2022. We do this by multiplying the projected biofuel production (in gallons) by the energy density of biofuels:
36 x 10^9 gallons/year x 3.785 L/gallon x 8.0 x 10^6 MJ/L = 1.09 x 10^21 MJ/year

Finally, we divide the biofuel energy by the total energy demand and multiply by 100 to get a percentage:
(1.09 x 10^21 MJ/year) / (129.8 x 10^21 MJ/year) x 100 = 0.0281 x 100 = 2.81%

Therefore, the answer is A, 2.8%. This target represents only a small fraction of our projected 2022 total energy demand, so it may not have a significant impact on decreasing our dependence on foreign oil.

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