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Using enthalpy of combustion

As [link] suggests, the combustion of gasoline is a highly exothermic process. Let us determine the approximate amount of heat produced by burning 1.00 L of gasoline, assuming the enthalpy of combustion of gasoline is the same as that of isooctane, a common component of gasoline. The density of isooctane is 0.692 g/mL.

A picture shows a large ball of fire burning on a road. A fire truck and fireman are shown in the foreground.
The combustion of gasoline is very exothermic. (credit: modification of work by “AlexEagle”/Flickr)

Solution

Starting with a known amount (1.00 L of isooctane), we can perform conversions between units until we arrive at the desired amount of heat or energy. The enthalpy of combustion of isooctane provides one of the necessary conversions. [link] gives this value as −5460 kJ per 1 mole of isooctane (C 8 H 18 ).

Using these data,

1.00 L C 8 H 18 × 1000 mL C 8 H 18 1 L C 8 H 18 × 0.692 g C 8 H 18 1 mL C 8 H 18 × 1 mol C 8 H 18 114 g C 8 H 18 × 5460 kJ 1 mol C 8 H 18 = −3.31 × 10 4 kJ

The combustion of 1.00 L of isooctane produces 33,100 kJ of heat. (This amount of energy is enough to melt 99.2 kg, or about 218 lbs, of ice.)

Note: If you do this calculation one step at a time, you would find:

1.00 L C 8 H 18 1.00 × 10 3 mL C 8 H 18 1.00 × 10 3 mL C 8 H 18 692 g C 8 H 18 692 g C 8 H 18 6.07 mol C 8 H 18 692 g C 8 H 18 −3.31 × 10 4 kJ

Check your learning

How much heat is produced by the combustion of 125 g of acetylene?

Answer:

6.25 × 10 3 kJ

Got questions? Get instant answers now!

Emerging algae-based energy technologies (biofuels)

As reserves of fossil fuels diminish and become more costly to extract, the search is ongoing for replacement fuel sources for the future. Among the most promising biofuels are those derived from algae ( [link] ). The species of algae used are nontoxic, biodegradable, and among the world’s fastest growing organisms. About 50% of algal weight is oil, which can be readily converted into fuel such as biodiesel. Algae can yield 26,000 gallons of biofuel per hectare—much more energy per acre than other crops. Some strains of algae can flourish in brackish water that is not usable for growing other crops. Algae can produce biodiesel, biogasoline, ethanol, butanol, methane, and even jet fuel.

Three pictures are shown and labeled a, b, and c. Picture a shows a microscopic view of algal organisms. They are brown, multipart strands and net-like structures on a background of light violet. Picture b shows five large tubs full of a brown liquid containing these algal organisms. Picture c depicts a cylinder full of green liquid in the foreground and a poster in the background that has the title “From Field to Fleet.”
(a) Tiny algal organisms can be (b) grown in large quantities and eventually (c) turned into a useful fuel such as biodiesel. (credit a: modification of work by Micah Sittig; credit b: modification of work by Robert Kerton; credit c: modification of work by John F. Williams)

According to the US Department of Energy, only 39,000 square kilometers (about 0.4% of the land mass of the US or less than 1 7 of the area used to grow corn) can produce enough algal fuel to replace all the petroleum-based fuel used in the US. The cost of algal fuels is becoming more competitive—for instance, the US Air Force is producing jet fuel from algae at a total cost of under $5 per gallon. For more on algal fuel, see http://www.theguardian.com/environment/2010/feb/13/algae-solve-pentagon-fuel-problem. The process used to produce algal fuel is as follows: grow the algae (which use sunlight as their energy source and CO 2 as a raw material); harvest the algae; extract the fuel compounds (or precursor compounds); process as necessary (e.g., perform a transesterification reaction to make biodiesel); purify; and distribute ( [link] ).

A flowchart is shown that contains pictures and words. Reading from left to right, the terms “Grow,” “Harvest,” “Extract,” “Process and purify,” and “Jet fuel gasoline diesel” are shown with right-facing arrows in between each. Above each term, respectively, are diagrams of three containers, three cylinders lying side-by-side, a pyramid-like container with liquid inside, a factory, and a fuel pump. In the space above all of the diagrams and to the left of the images is a diagram of the sun.
Algae convert sunlight and carbon dioxide into oil that is harvested, extracted, purified, and transformed into a variety of renewable fuels.

Questions & Answers

what do you mean by d block ,give more details element
Agburum Reply
Define chemical formula
Kevin Reply
they are the mathematical representation of chemicals I guess
Uche
Bohr model of hydrogen atom
Muhammad Reply
what is important of this model
nagesh
what is the main reaction between sodium and chlorine
Akeem Reply
when a sodium atom is transferred an electron to a chloride atom forming a sodium cation and a chlorde anoin both ions are compltely valence shells and a energetically more stable this reaction is extremely more exothermic producing a bright yellow light abd a great deal of heat energy
sani
well what kind of sodium
coland
sodium chloride
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Sodium picosulfate (INN, also known as sodium picosulphate) is a Contact stimulant laxative used as a treatment for constipation or to prepare the large bowel before colonoscopy or surgery. It is sold under the trade names Sodipic Picofast, Laxoberal, Laxoberon, Purg-Odan, Picolax, Guttalax, Namilax
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Ipodate sodium (sodium iopodate) is an iodine-containing radiopaque contrast media used for X-rays. The drug is given orally and the resulting contrast allows for easy resolution of the bile duct and gall bladder. Other uses Although not FDA approved, ipodate sodium has been used to treat Graves'
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i think some was missed
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what chlorine L-Alpha glycerylphosphorylcholine (alpha-GPC, choline alfoscerate) is a natural choline compound found in the brain. It is also a parasympathomimetic acetylcholine precursor which may have potential for the treatment of Alzheimer's disease and other dementias. Alpha-GPC rapidly delive
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Choline (/ˈkoʊlin/) is a water-soluble vitamin. It is usually grouped within the B-complex vitamins. The term cholines refers to the class of quaternary ammonium salts containing the N,N,N-trimethylethanolammonium cation (X− on the right denotes an undefined counteranion). The cation appears in the
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thanks
sani
please what is redox reaction
BABARINDE
hydrogen reacting with water
Iyenge Reply
what is matter
Godgift Reply
apart from those device there is there any device
Eke Reply
how many elements do we have
ARUOTURE Reply
Modern Electronic Theory
Levi Reply
a new way or an improvement in modern electrical products.
Andrew
find the volume of oxygen produced from the electrolysis of acidified water of a current of a 2A was passed through the electrolysis of acidified water for 2 hours
Ngwu Reply
14400J
Ese
wrong question, go through it. oxygen cannot be produced.
Andrew
A group of atoms that are connected by chemical bounds
Valerie Reply
molecule
NARCOS_
the atoms are found in the shell, it is called atomic bond.
Andrew
what is molecules
Kelly Reply
what atoms
Simon
Moecules are groups of atoms
Adewole
atom is the smallest part of an element or matter that indivisible
Ese
What is collision theory
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joules
udoh
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Source:  OpenStax, Chemistry. OpenStax CNX. May 20, 2015 Download for free at http://legacy.cnx.org/content/col11760/1.9
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