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Alkanes are used primarily as __, __ and __/
Alkanes are __, so they dissolve in __ or __ solvents.
Alkanes are said to be __. Why?
- weakly polar organic solvents
- hydrophic because they do not dissolve in water
Alkanes are good __ and __ for metals because they keep water from reachign the metal surface and causing __.
- lubricants and preservatives
Alkanes have densities around __ compared with a density of __ for water. Because of the fact they are __ adn __, a mixture of alkane and water separates into two phases, with __ on top.
- .7 g/mL
- 1.0 g/mL
- less dense
- insoluble in water
The BP of alkanes increase smoothly with __ and __.
increasing number of carbon atoms and increasing MW
Larger molecules have larger __, resulting in increased __. These increased attractions must be overcome for __ and __ to occur. Thus, a larger molecule, with a greater surface area and greater van der Waals attractions, boils at a __ temperature.
- intermolecular van der Waals attractions
- vaporization and boiling
- higher temp
BP increases with __. Each additional CH2 group increases the BP by about __ up to ten carbons, and by about __ in higher alkanes.
- increasing MW
- 30 degrees C
- 20 degrees C
Explain BP in terms of branched.
In general, a branched alkane boils at a lower temperature than the n-alkane with the same number of carbon atoms. This difference in BP arises because branched alkanes are more compact, with less SA for London force interactions
MPs increase with __. The MP graph, however, is not __.
Alkanes with even numbers of carbon atms do what, so that what?
pack better into a solid structure so that higher temps are needed to melt them
Alkanes with odd numbers do what, so that what?
do not pack as well adn they melt at lower temperatures
__ of petroleum separates alkanes into __ with __.
These fractions are suited for different uses based on their __, such as __ and __.
- similar BP
- physical properties
- volatility and viscosity
Methane and ethane are __ at room temp and atmospheric pressure. They are __, so they are usually handled as __.
Upon cooling to cryogenic (very low) temperature,s methane and ethane become __.
__, mostly methane, can be transported in special refrigerated tankers more easily than it can be transported as a compressed gas.
- difficult to liquefy
- compressed gases
- liquefied natural gas
Propane and butane are __ at room temp and pressure, but they are easily __ at room temp under modest pressure.
These gases, often obtained along with liquid petroleum, are stored in low-pressure cylinders of __.
- liquefied petroleum gas (LPG)
Propane and butane are __, both for __ and __. They __ cleanly, and pollution-control equipment is rarely necessary. In many agricultural areas, propane and butane are more cost-effective tractor fuels than gasoline and diesel fuel.
- good fuels
- for internal combusion engines
Propane and butane have largely replaced __ as propellants in aerosol cans. Unlike alkanes, the __ are implicated in damaging the earth's protective ozone layer.
- chlorofluorocarbon Freon propellants
The next four carbons are __, __. Isomers of pentane, hexane, heptane, and octane are the primary constituents of __. Their __ is crucial for this use because the injection system simply squirts a stream fo gasoline into the intake air as it rushes through.
- free-flowing, volatile liquids
If gasoline did not __ easily, it would reach the cylinder in the form of droplets, which cannot burn as efficiently as a vapor, so the engine would smoke and give low mileage.
In addition to being __, gasoline must resist the potentially damaging explosive combustion known as __. The __ properties of gasoline are rated by an __ that is assigned by comparing the gasoline to a mixture of n-heptane (which __ badly) and isooctane (which is not prone to __).
The gasoline being tested is used in a test engine with a variable __ ratio.
- octane number
Higher compression ratios induce what, so the compression ratio is increased until what begins.
The octane number assigned to the gasoline is simply what?
the percentage of isooctane in an isooctane/ heptane mixture that begins to knock at that same compression ratio
The nonanes through about the hexadecanes (C16) are __ that are somwhat __. These alkanes are used in __ (3)___.
- higher- boiling
- jet fuel
- diesel fuel
__, the lowest-boiling of these fuels, was once widely available but is now harder to find. It is less __ than gasoline, and less prone to forming __ mixtures.
__ was used in __ and __, which use wicks to allow this heavier fuel to burn. Jet fuel is similar to __, but more highly __ and less __.
- kerosene lamps
Diesel fuel is not very __, so it does not __ in the intake air. In a diesel engine, the fuel is sprayed directly into the cylinder right at the top of the __.
The hot, highly compressed air in the cylinder causes the fuel to __.
- compression stroke
- burn quickly, swirling and vaporizing as it burns
Some of the alkanes in diesel fuel have fairly __, and they may __ in cold weather. This __ causes the diesel fuel to turn into a waxy, semisolid mass. Owners of diesel engines in cold climates often mix a small amount of gasoline with their diesel fuel in the winter. The added gasoline does what?
- high freezing points
- partial solidification
- dissolves the frozen alkanes, diluting the slush and allowing it to be pumped to the cylinders
ALkanes with more than sixteen carbons are most often used as __ and __. These are sometimes called __ because they come from __, which was once considered a mineral.
- lubricating and heating oils
- mineral oils
__ is nto a true wax, but a purified mixture of high-M-W alkanes with __ well above room temp. The true waxes are __.
- paraffin "wax"
- long-chain esters
Alknaes are derived mostly from __ and __ byproducts.
__, often called __, is pmped from wells that reach into pockets contain ing the remains of prehistoric plants.
- petroleum x2
- crude oil
The principal constituents of crude oil are __, some __, and some __. The composition of petroleum and the amounts of contaminants vary from one source to another, and a __ must be carefully adjusted to process a particular type of __. Because of their different qualities, different prices are paid for light Arabian crude, West Texas crude, adn other classes of crude petroleum.
- some aromatics
- some undesirable compounds containing S and N
- crude oil
The first step in refining petroleum is __. The products of __ are not __ but __ with useful ranges of BP.
- a careful fractional distillation
- the distillation
- pure alkanes
- mixtures of alkanes
After distillation, __ converts some of the less valuable fractions to more valuable products. __ involves heating alkanes in the presence of materials that catalyze the __ of large molecule sinto smaller ones.
- catalytic cracking x2
__ is often used to convert __ into mixtures that can be blended with gasoline. When cracking is done in the presence of __ (__), the product is a mixture of __ free of S and N impurities.
- higher-boiling fractions
- hydrogen (hydrocracking)
__ was once treated as a waste product of __ and destroyed by flaring it off. Now __ is an equally valuable natural resource, pumped and stored throughout the world.
- natural gas
- petroleum production
- natural gas
Natural gas is about __(percentages)__, depending on the source of the gas.
Small amounts of other __ and __ are also present.
Natural gas is often found above __, although it is also found in places where there is little or no recoverable __ or __.
- 70% methane; 10% ethane; 15% propane
- hydrocarbons and contaminants
- pockets of petroleum or coal
- petroleum or coal
Natural gas is used primarily as?
It is also important as __.
- a fuel to heat buildings and to generate electricity
- starting material for the production of fertilizers.
Although the __ we burn as natural gas is millions of years old, another 300 million tons per year of new methane is synthesized by __ of diverse places such as stomachs of plant-eating animals and hte mud under hte seafloor.
Most of the undersea __ is eaten by other microbes, but some escapes at __.
Under the sea, cold, high-pressure conditions may allow formation of __, with individual __ molecules trapped inside cages of water molecules.
- methane seeps
- methane hydrate
When __ is brought to the surface, it quickly melts and the methane escapes. We currently have no practical methods for capturing and using microbial __ or __. Much of this __ escapes to the atmosphere, where it acts as a __ and contributes to __.
- methane hydrate
- methane or methane hydrate
- greenhouse gas
- global warming
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