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Chemistry > Topic 7-Organic Chemistry > Flashcards

Topic 7-Organic Chemistry Flashcards

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1
Q

What two types of atoms are hydrocarbons made out of?

A

Hydrogen and carbon

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2
Q

What is crude oil?

A

Crude oil is a mixture of compounds

It is a finite resource found in rocks and is the remains of ancient biomass consisting mainly of plankton that was buried in mud

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3
Q

What is a hydrocarbon?

A

A compound made up exclusively of hydrogen and carbon atoms

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4
Q

What are alkanes?

A

They are saturated hydrocarbons meaning there are only single bonds present in the molecule

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5
Q

What is the general formula for alkanes?

A

CnH2n+2

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6
Q

What is a homologous series?

A

A ‘family’ of organic compounds that have the same functional group and similar chemical properties

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7
Q

What are the first 4 alkanes?

A

Methane, ethane, propane and butane

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8
Q

Describe the combustion of hydrocarbons

A

Exothermic reaction occurring when hydrocarbons are reacted with oxygen

Complete combustion produces carbon dioxide and water (carbon and hydrogen atoms are completely oxidised)

Incomplete combustion produces carbon or carbon monoxide and water

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9
Q

Define the combustion of hydrocarbons

A

Exothermic reaction occurring when hydrocarbons are reacted with oxygen

Complete combustion produces carbon dioxide and water (carbon and hydrogen atoms are completely oxidised)

Incomplete combustion produces carbon or carbon monoxide and water

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10
Q

Describe the physical properties of alkanes

A

First few in series are gases, then change to liquids, then to solids

In general, boiling points and viscosity increase as molecules get bigger

Volatility and flammability decrease as molecules get bigger

Poor reactivity

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11
Q

Explain how fractional distillation of crude oil takes place

A

Crude oil is heated up and vaporised. The hot crude oil is pumped into the column.

The column has a temperature gradient and is hot at the bottom and cooler at the top

The long chain molecules have higher boiling points because there are stronger intermolecular forces between their longer chains.

Shorter hydrocarbons have low boiling points because there are fewer intermolecular forces between their chains

The smaller molecules condense at the top of the column at the top of the column where the temperature is cooler.

Hydrocarbons of similar length will be collected in the same tray and are known as fractions

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12
Q

What is cracking?

A

When large hydrocarbons are thermally broken down into smaller and useful molecules

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13
Q

What type of reaction is cracking?

A

Thermal decomposition

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14
Q

What are the conditions needed for catalytic cracking and what is it useful for?

A

Low pressure

500 degrees Celsius

Useful for producing petrol

You need to have a catalyst

Makes branched alkanes

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15
Q

What are the conditions needed for thermal cracking and what is it useful for?

A

High pressure

High temps (450-750)

Makes lots of alkenes

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16
Q

How are the products used?

A

The products are alkanes and alkenes-used as polymers and starting materials for synthesis

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17
Q

What is an alkene?

A

Unsaturated hydrocarbon

Contains a C=C bond

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18
Q

What is the general formula for alkenes?

A

CnH2n

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19
Q

What is the test for alkenes?

A

Add bromine water.

Colour change occurs from orange to colourless

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20
Q

Describe the combustion of alkenes

A

They burn with smoky flames due to incomplete combustion

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21
Q

Describe the addition reactions of alkenes (3 processes)

A

a) With hydrogen-hydrogenation; requires a higher temperature and a nickel catalyst
b) With steam- hydration; requires high temperature, pressure, and concentrated phosphoric acid as a catalysts
c) With Br2/Cl2/I2-Addition of halogens

22
Q

What is an alcohol?

A

An organic compound that contains an -OH functional group

23
Q

State characteristics of methanol, ethanol, propanol and butanol?

A

Dissolve in water to form a neutral solution

React with sodium to form hydrogen

Burn in oxygen

React with carboxylic acids in presence of acid catalyst to form ester

24
Q

Oxidation of the alcohols leads to…

A

Carboxylic acids

25
Q

What are some uses of alcohols?

A

Fuels

Solvents

Drinks

26
Q

State the conditions required for fermentation of glucose and state the equation of the reaction?

A

30 degrees Celsius

Aqueous solution of the glucose

Yeast added

Absence of air

27
Q

What are carboxylic acids?

A

Organic compounds that contain a COOH functional group

28
Q

State characteristics of carboxylic acids

A

Dissolve in water to form an acidic solution (contains H+ ions)

React with metal carbonates to form carbon dioxide

React with alcohols with an acid catalyst to produce esters

React with metals to give off hydrogen gas

29
Q

What type of acid is carboxylic acid?

A

It is a weak acid

30
Q

Explain why carboxylic acids are weak acids?

A

They are partially dissociated in water.

Thus, the pH of a carboxylic acid in solution is not as low as a solution of a strong acid of the same concentration

31
Q

What is an ester and how is it formed?

A

An organic compound containing a COO- functional group, formed from carboxylic acid and alcohol in the presence of a sulfuric acid catalyst

They have a fruity smell

32
Q

What is a polymer? How do molecules containing C=C bond form polymers?

A

A polymer is a long chain molecule which is made by lots of smaller molecules joining together

C=C bonds open up and many smaller molecules (monomers) join together to form a chain (a polymer).

No other products are made

It is called an ‘addition polymerisation’ reaction

33
Q

Give 3 examples of addition polymers and their uses

A

Polyethene-plastic bags

(Poly)tetrafluoroethene-teflon surfaces, for use in non-stick kitchenware

(Poly)chloroethene (PVC)-water pipes

34
Q

What is a repeating unit of a polymer?

A

It is a smallest structure which, upon numerous translations, yields the structure of the polymer

In ‘addition polymers’: to draw it, take a monomer, change C=C to C-C and show additional single bonds extending away from these carbons

35
Q

What is a condensation polymer? How is it made?

A

It is a polymer made in condensation polymerisation

In this reaction, many molecules join together; the polymer is formed, but also a small molecule is released

36
Q

What are the two types of condensation polymers-name them and give industrially relevant examples

A

Polyesters-Terylene

Polyamides-Nylon

37
Q

What is an amide bond?

A

An amide bond is similar to the ester bond, with O replaced by N

(C=O)-NH2

Just like an ester, it contains the C=O group

38
Q

What is an amino acid?

A

It is an organic compound that contains both a carboxylic acid functionality (COOH) and an amine functional group (NH2)

39
Q

How do amino acids make protiens?

A

By numerous condensation polymerisation reactions; proteins are polymers made of amino acids (monomers)

40
Q

What are polypeptides?

A

Polypeptides are also made by condensation polymerisation of amino acids, but are shorter than proteins

One could think about proteins as a product of many polypeptide chains bonded together

41
Q

What are carbohydrates?

A

They are organic molecules made of C, H and O

They are biologically relevant (starch and cellulose)

Both of these are polymers made of glucose monomers

Their structure differ in the way the glucose molecules are joined together

42
Q

What is DNA? Describe its role and structure

A

DNA is a material that makes up chromosomes-cell structures that store genetic information

DNA is made of two polymer chains that are held together in a double helix

Each polymer chain can be made from 4 different monomers - nucleotides

43
Q

Cars use sulfur-free petrol as a fuel

Describe why sulfur should be removed from petrol

A

Burning sulfur produces sulfur dioxide when it reacts with oxygen

This causes acid rain

44
Q

Describe and explain how petrol is separated from the mixture of hydrocarbons in crude oil

A

The process used is fractional distillation

Most of the hydrocarbons evaporate and form vapours or gases.

Vapours rise up the fractioning column and cool as they do so

When a fraction of the hydrocarbons cool to their boiling point they condense

Hydrocarbons that have relatively low boiling points are collected near the top of the fractioning column (and vice versa)

Hot at top and cool at bottom (temp. gradient)

45
Q

State how nitrogen oxides are produced in a petrol engine

A

Nitrogen and oxygen are in the air and react at high temperatures (bonds)

46
Q

Explain why clearing large areas of forest has an environmental impact on the atmosphere

A

Less CO2 is absorbed from atmosphere

Burning trees releases co2

47
Q

Describe and explain how the composition of the Earth’s atmosphere was changed by the formation of coal

A

Carbon dioxide decreased by plants and trees

Oxygen is increased by plants/trees

Because coal stores carbon dioxide

48
Q

Explain why, in the terms of energy involved in bond breaking and bond making, the combustion of methane is exothermic

A

Energy is taken in to break the bonds

Energy is given out when bonds are made

Energy given out is greater than energy taken in

49
Q

Crude oil is a fossil fuel

Describe how crude oil is separated into fractions

A

Heated to evaporate hydrocarbons

Hotter at the top and cooler at the bottom (temperature gradient)

Vapours condense at different levels

50
Q

Some polymers are described as smart polymers

Suggest one property of smart polymer that is different to that of an ordinary polymer

A

Has a shape memory

Can return to original shape when conditions change

Chemistry (10 decks)

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