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chemistry > Chemistry unit 7 > Flashcards

Chemistry unit 7 Flashcards

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1
Q

What is crude oil and how is it formed

A

a recourse found in the earth made from ancient biomass that has been underground for a long time. It is a mixture of lots of different compounds, all mostly hydrocarbons

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2
Q

What is a hydrocarbon

A

A substance made up of only hydrogen and carbon

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3
Q

What is a mixture

A

2 or more elements not chemically bonded together but physically together. the elements still have their individual properties

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4
Q

How do we separate substances in a mixture

A

via distillation methods like fractional distillation

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5
Q

What is an alkane

A

A saturated hydrocarbon with carbon-carbon single bonds

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6
Q

What does it mean if a substance is saturated

A

carbon-carbon single bonds

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7
Q

What is a homologous series

A

A group of compounds which share similar formulas, have the same functional group and have similar chemical properties. e.g. Alkane

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8
Q

What is a functional group

A

The atoms in a substance that determine which homologous series it is in

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9
Q

general formula for alkanes

A

CnH2n+2

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10
Q

name the first 4 alkanes

A

methane, ethane, propane, butane

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11
Q

How many bonds does each carbon have?

A

4

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12
Q

Describe the process of fractional distillation

A

-Crude oil is heated to very high temperatures in the fractioning column and it is vapourised so the crude oil is a gas
-Each fraction of hydrocarbon has a different boiling point so they will condense at different levels in the fractional column so they are separated and can then be tapped off for use.
-The largest hydrocarbons form at the bottom and the smallest form at the top of the column

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13
Q

What is the use of this industrial fractional distillation of hydrocarbons

A

-we use many of the fractions that we get off like kerosene or gasoline for fuels
-we get other products that are useful in the petrochemical industry as solvents or polymers

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14
Q

What is a fuel

A

A recourse that when burned, produces heat energy

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15
Q

How does the sizes of hydrocarbons affect their properties

A

-The larger the hydrocarbon, the higher the boiling point
-The larger the hydrocarbon is, the less flammable it is
-The larger the hydrocarbon is, the dirtier the flame produced is
-The larger the hydrocarbon is, the more viscous it is

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16
Q

What are the products when we burn hydrocarbons

A

Carbon dioxide + water (complete combustion with sufficient oxygen)
Carbon (Monoxide) + water (incomplete combustion with not enough oxygen present)

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17
Q

What properties should a good fuel have

A

-Clean flame to burn
-high flammability
-low boiling point

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18
Q

How do we test to see whether combustion has taken place from a hydrocarbon

A

When the heat is put through the funnel and down the tubes, the ice bath will condense the water vapour and we can confirm its Prescence by hydrating anhydrous copper sulphate.
We put limewater at the end of the tube so that when the CO2 reaches it, it will turn cloudy.
we have proved the Prescence of Water and CO2 so complete combustion has taken place.

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19
Q

What is the process of cracking ? Why do we do it

A

When we break up larger alkanes into a smaller alkane and an alkene. There is a greater demand for small chain alkanes and alkenes can be used to make polymers.

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20
Q

What can we use long chain alkanes for

A

Road tar like bitamine

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21
Q

What is an alkene

A

An unsaturated hydrocarbon with 1Carbon=Carbon Double bond

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22
Q

What conditions and process done in order to carry out cracking

A

-The hydrocarbon is vapourised at around 800’C and passed over a zeolite catalyst (catalytic cracking)
-Or we can mix the hydrocarbon with steam at very high temperatures so thermal decomposition happens (steam cracking)

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23
Q

general formula for alkenes

A

CnH2n

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24
Q

name the first 4 alkenes

A

ethene, propene, butene, pentene

25
Q

how do we test for a alkene

A

-We put it in bromine water and the alkene will decolourise the bromine water as alkenes are more reactive than alkanes. forms dibromoethane.

26
Q

what happens when we burn alkenes

A

They undertake incomplete combustion so they burn with a smoky, yellow flame. As carbon soot is produced, burning alkenes can lead to global dimming so the planet gets cooler

27
Q

in alkene reactions, what happens to the Carbon=Carbon double bond

A

It opens up

28
Q

What is an addition reaction

A

When two smaller molecules e.g. Ethene + bromine, add together to make a larger molecule, e.g. dibromoethane. All of the organic chemistry reactions are addition reactions

29
Q

What happens when we react an alkene with hydrogen and under what conditions do we do it

A

Hydrogenation. at 60’C and with a nickel catalyst, an alkene and hydrogen react to form an alkane. It saturates the solution.

https://www.thoughtco.com/definition-of-hydrogenation-604530

30
Q

What happens when we react an alkene with steam and under what conditions do we do it

A

Hydration. at 300’C and at 65atm of pressure with an concentrated phosphoric acid catalyst. An alkene and Hydrogen react together to form an alcohol.

31
Q

How else can we produce an alcohol (ethanol)

A

Fermentation where glucose is turned into ethanol and carbon dioxide. 30’C at one 1 atm of pressure with yeast catalyst

32
Q

Name the first 4 alcohols

A

methanol, ethanol, propanol, butanol

33
Q

Compare fermentation to hydration

A

-Fermentation takes longer but it is renewable unlike hydration
-We need low conditions for fermentation compared to hydration
-a lot of labour needed for fermentation but little for hydration
-Fermentation requires batch production but hydration is continuous.
-fermentation provides impure by-products unlike hydration

34
Q

Describe reactions of alcohols in these substances:
-Water
-air
-sodium
-oxidising agents

A

-water: dissolve in water to produce a neutral solution
-air: burns in air to produce CO2 + water
-sodium: produces a salt + hydrogen
-Oxidising agents eg oxygen- reacts to form carboxylic acids

35
Q

Uses of the first 4 alcohols

A

methanol: used in antifreeze and in feedstock
ethanol: the main alcohol in alcoholic drinks
all 4: Used as fuels

36
Q

What is the functional group for carboxylic acids

A

COOH

37
Q

name the first 4 carboxylic acids

A

methanoic acid, ethanoic acid, propanoic acid, butanoic acid

38
Q

What is the functional group for alcohol

A

O-H

39
Q

Reactions of the first 4 carboxylic acids

A

-Dissolve in water to produce acidic solutions
-React with metal carbonates to form Salt, water and CO2
-reacts with alcohols with an acid catalyst to produce an ester

40
Q

Why are carboxylic acids weak acids

A

They don’t completely ionise in water so they don’t release many H+ ions. They have a higher pH (around 5) than other acids of the same concentration

41
Q

What is the functional group for esters

A

COO

42
Q

What is the primary characteristic of an ester and its use

A

Fruity Smell so we use it in artificial flavourings and perfumes

43
Q

How do we name an ester

A

-We put the name of the acid first and change the ending to yl
Then we add the name of the carboxylic acid and add oate on the end
e.g. Ethyl ethanoate has ethanol ethanoic acid

44
Q

What is a polymer

A

A very large chain of covalently bonded molecules,
These molecules are called monomers and they are often alkenes

45
Q

give some examples of polymers

A

-Polyethene, polypropene, polybutene

46
Q

How do we write out the structural formula for a polymer in addition polymerisation

A

Write the alkene structural formula in brackets with an n outside the brackets to show that it is repeating over and over.
You need to draw the bonds coming out of the acid to show that it is continuing.
The carbon=carbon double bond is broken

47
Q

Difference between addition polymerisation and condensation polymerisation

A

there can be multiple products formed in condensation polymerisation, most notably water or hydrogen chloride

48
Q

Why are multiple products formed in condensation polymerisation

A

it is the joining together of monomers with 2 different functional groups (not alkenes) and sometimes molecules are lost which leads to the water forming

49
Q

How to draw a condensation polymer

A

put two groups of the same functional group on either side of the polymer, then draw a box in the middle .
Do this for both monomers.
react the two monomers together (remembering water will form) to make longer chains of the polymer
e.g. COOH-box-HOOC + HO-box-OH -> HO-box-OOC-box-COO-box-OOC-box-COO-box-OH + H2O.
n HO-■-OH + n HOOC-♦-COOH

50
Q

How do we write a condensation polymer in shorthand

A

-we take a 2 adjacent monomer units in the polymer and put them in the same special bracket for addition polymerisation.
then we put n outside the bracket.
-remember to add 2nH2O at the end.
(-■-OOC-♦-COO-)n + 2n H2O

51
Q

How do we form a polyester

A

Combining a diol (e.g. ethanediol) with a dicarboxylic acid (e.g. hexanedioic acid) to produce a polyester

52
Q

What is DNA

A

a large molecules that is essential for life and codes for all genetic instructions in organisms for development and function

53
Q

What is the structure of DNA like

A

most molecules are 2 polymer chains made of 4 different monomers called nucleotides (A,T,C and G), shaped in a double helix

54
Q

Name some other naturally occurring polymers that are essential for life

A

-Proteins with amino acid monomers
-Starch with glucose monomers
-Cellulose with glucose monomers

55
Q

What are amino acids

A

Monomers with 2 different functional groups in a molecule (amine’s and carboxylic acids)

56
Q

What do they produce when they react via polymerisation reactions

A

polypeptides e.g. glycine (H2NCH2COOH)
works like making polyesters but with different functional groups

57
Q

how do we write out the condensation polymerisation formula for glycine

A

(HNCH2CO)n + nH2O

58
Q

How are proteins produced

A

When different amino acids combine in the same chain

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