Chemistry Test

Midterm Chemistry Test- please don't screw up

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What is crude oil?
Crude oil is a mixture of different compounds which boil at different temps.
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What can distillation be used for?
Separating a mixture of liquids
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What is the name of the liquids produced by simple distillation
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What are alkanes?
Alkanes are saturated hydrocarbons
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The formula to work out how many hydrogens in an alkane is...?
the amount of carbons x2 +2, so 2n+2
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What is the name of the process which separates mixtures in crude oil, and is used in refineries?
Fractional distillation
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Finish of this phrase: The larger the hydrocarbon molecule...?
The higher its boiling point
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Describe and explain the process of fractional distillation in crude oil?
1.) Crude oil is vaporised, fractionating column. 2.) Vapours move up columns. 3.) Hydrocarbons condense to liquids when reaching their boiling point. 4.) Different liquids collect on trays- outlets to their fractions
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Summarise what type of hydrocarbons end up where in a fractionating column *hint:larger hydrocarbons are found at the...
larger hydrocarbons= bottom or near the bottom of the fractionating tower and vice versa for smaller hydrocarbons
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What is the difference between simple distillation and fractional distillation?
simple distillation- done in steps, heating the mixture to different temps. Fractional distillation= continuously vaporising mixture and condensing fractions at different temps.
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Properties of fractions?
Fractions with low boiling ranges= less thick (low viscosity). Very flammable, clean flames (little smoke)- very useful as fuels
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Write a word equation for the complete burning of a pure hydrocarbon
hydrocarbons+ oxygen (burning) → carbon dioxide+ water
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What happens if there is a limited supply of air? Possible products?
Incomplete combustion. Carbon monoxide, solid particles that contains soot (carbon on its own), particulates (unburnt hydrocarbons)
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List 2 reasons why the burning of fossil fuels could potentially cause acid rain.
Most fossil fuels contain sulphur compunds. When burnt, these sulphur compunds produce sulphur dioxide. Sulphur dioxide. As a result of the high temps. produced when fuels burn, oxygen and nitrogen in the air may combine to form nitrogen oxide
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List 2 possible effects on the environment as a result of burning large amounts of fuels
1.) fuels that contain carbon= carbon dioxide- global warming. 2.) carbon monoxide from incomplete combustion is poisonous. 3.) acid rain from sulphur dioxide OR nitrogen oxides. 4.) tiny solid particulates that reflect sunlight causes global dimming
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How do we tackle any of these problems? (only one solution is needed)
1.) Sulphur dioxide is removed from the waste gases in power stations. 2.) Sulphur dioxide can be removed before it is supplied to users. 3.) catalytic converters in cars remove carbon dioxide and nitrogen oxides. 4.) Filters can remove particulates
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What are biofuels? *tip: know at least 2 biofuels e.g. biodiesel and ethanol + acknowledge the potential of hydrogen being used in the future!
Renewable fuels made from plant or animal products
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What is biodiesel made from? *tip: you don't need to know an advantage and disadvantage BUT should be able to evaluate info. given in an exam!
Made from vegetable oils extracted from plants.
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What is cracking hydrocarbons?
Breaking large hydrocarbon molecules into smaller molecules
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List the two ways in which cracking can be done
1.) heating a mixture of hydrocarbon vapours with steam to a very high temp. 2.)passing hydrocarbon vapours over a hot catalyst.
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As a result of cracking, some small alkane molecules are produced. Give one reason why an oil company might want to crack large hydrocarbons to produce smaller alkanes? *hint: think about its properties...
alkanes with smaller molecules are more useful as fuels
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What is the name of unsaturated hydrocarbons?
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The general formula for an alkene is...
C(n) H(2n)
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Give 3 ways in which alkenes are different from alkanes.
1.) less hydrogen atoms. 2.) double-bonded. 3.) more reactive
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When alkenes react with bromine water, from orange, the water turns...
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Card 2


Separating a mixture of liquids


What can distillation be used for?

Card 3




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Card 4


Alkanes are saturated hydrocarbons


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Card 5


the amount of carbons x2 +2, so 2n+2


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