Topic 9 - Hydrocarbons, Alcohols, Carboxylic Acids, Polymers

Question 1

hydrocarbons

Answer 1

molecular compounds that contain only carbon and hydrogen

Question 2

alkanes general formula

Answer 2

CnH2n+2

Question 3

When are molecules saturated

Answer 3

When all the carbon-carbon covalent bonds are single bonds

Question 4

When are molecules unsaturated?

Answer 4

When they contain at least one double covalent bond between adjacent carbon atoms

Question 5

alkenes general formula

Answer 5

CnH2n

Question 6

What bonds do alkenes have?

Answer 6

carbon-carbon double bond

Question 7

isomers

Answer 7

Molecules with the same molecular formula, the different arrangements of atoms

Question 8

What do numbers in isomers show?

Answer 8

The position of the double bond

Question 9

What is formed in the complete combustion of a hydrocarbon?

Answer 9

Only carbon dioxide and water is formed when there is a plentiful supply of oxygen

Question 10

What gets produced in incomplete combustion?

Answer 10

If there is an insufficient amount of oxygen, full oxidisation does not occur and carbon (soot) and carbon monoxide can be formed as well as water and carbon dioxide

Question 11

When and how is the bromine water test used?

Answer 11

To tell the difference between alkenes and alkenes because ALKANES do not react with it (cause decolourisation)

Question 12

what and why is the colour change in the bromine water test if an alkene is detected

Answer 12

the orange-brown colour turns colourless because the C=C double bond reacts with the bromine to form a colourless product, bromine is therefore removed from the solution which looses it colour (hence why it doesn’t work with alkenes because they don’t have a double bond)

Question 13

addition reaction

Answer 13

Reaction in which reactants combined to form one larger product molecule and no other products

Question 14

fermentation

Answer 14

• Plant material containing sugars is mixed with water and yeast -> enzymes in the yeast, turn the sugars into ethanol and carbon dioxide

Question 15

What do the percentages mean in alcohols

Answer 15

How much ethanol they have

Question 16

How is ethanol made?

Answer 16

Through fermentation (sugars)

Question 17

Why is an airlock in the neck of a jar when making ethanol necessary (fermentation)?

Answer 17

Allow carbon dioxide to escape while keeping air out; this is necessary because yeast fermentation is a type of anaerobic respiration and only occurs in the absence of oxygen

Question 18

What is fractional distillation of an ethanol solution needed if the concentrations are higher than 15%?

Answer 18

Cause higher concentrations kill the yeast cell

Question 19

How is a fractional distillation column used for ethanol % above 15?

Answer 19

• Ethanol boiling point (78°C) is lower than the boiling point of water (100°C)
• The heated liquids evaporate and their vapour cool as they rise up the fractionating column
• Cause the ethanol has a lower boiling point it remains a gas for longer and separates from the water -> as a result the first fraction that is collected contains a higher percentage of ethanol

Question 20

What do alkanes end in

Answer 20

-ane

Question 21

what do alkenes end in

Answer 21

-ene

Question 22

what do alcohols end in

Answer 22

-anol

Question 23

alcohol general formula

Answer 23

CnH2n+1OH

Question 24

Chemical properties of alcohols

Answer 24

• Produces carbon dioxide and water on complete combustion
• Can be oxidised to form compounds called carboxylic acid
• Reacts with reactive metals, forming hydrogen gas is one of the products

Question 25

Functional group

Answer 25

The atom of group of atoms in a molecule that is responsible for its main chemical reactions

Question 26

Why do alcohols have similar chemical properties?

Answer 26

Because they all contain one -OH functional group

Question 27

What are the uses of alcohol?

Answer 27

• solvents for cosmetics, medical drugs, varnishes
• Methanol and ethanol a widely used fuels and can be made from renewable sources

Question 28

What is the method for the combustion of alcohols (CORE PRACTICAL)

Answer 28

• Measure the mass of an alcohol burner and cap; record the mass and the name of the alcohol
• Place the alcohol burner in the centre of a heat resistant mat
• Using the measuring cylinder to add 100 cm³ of cold water to a conical flask
• Measure and record the initial temperature of the water and clamp the flask above the alcohol burner
• light the wick of the burner and allow the water to heat up by about 40°C
• Replace the cap on the burner and measure and record the final temperature of the water
• Measure the mass of the alcohol burner and cap again and record the mass
• Calculate the mass of the alcohol burned to produce a 1°C rise in temperature
• repeat all steps using fresh cold water and a different alcohol

Question 29

carboxylic acid general formula

Answer 29

CnH2n+1COOH

Question 30

How are carboxylic acids usually formed?

Answer 30

By the gentle oxidisation of alcohols using oxidising agents such as hot copper oxide

Question 31

What are the chemical properties of carboxylic acids?

Answer 31

• form solutions with a pH less than 7 (if soluable)
• React with metals to form a salt and hydrogen
• React with bases to form salt and water
• react with carbonates to form a salt, water and carbon dioxide
  -> acidic properties due to the presence of -COOH functional group