Summer Assessment 3- more

Question 1

how can you work out the speed of a reaction on a graph

Answer 1

• by recording the amount of product formed or the amount of reactant used up over time
• the steeper the line on a graph the fatser the reaction
• line becomes less steep as reactants are used up

Question 2

what do the quickest reactions show on a graph

Answer 2

-they have the steepest line and become flat in the least time

Question 3

what does the rate of a chemical reaction depend on

Answer 3

• collision frequency of reacting particles- the more collisions the faster the reaction
• energy transferred during a collision

Question 4

what is activation energy

Answer 4

-the minimum amount of energy particles need to react

Question 5

why to particles need activation energy

Answer 5

-to break the bonds in reactants to start to the reaction

Question 6

explain the method you would carry out to measure how surface area affects rate

Answer 6

• use marble chips and HCL
• set up the apparatus so you have a conical flask with marble chips in it as well as HCL- attach to the bung in the conical flask a gas syringe
• measure volume of gas produced using a gas syringe
• take readings at regular intervals and record the results

Question 7

why does using finer particles of solid mean a higher rate of reaction

Answer 7

-as finer particles mean the marble has a larger surface area

Question 8

what effect does changing the concentration of acid have on the rate of reaction

Answer 8

a higher concentration gives a faster reaction

Question 9

what is the general formula for alkenes

Answer 9

CnH2n

Question 10

what is the empirical formula (for ethene)

Answer 10

CH2

-simplest ratio of atoms

Question 11

what is the molecular formula (for ethene)

Answer 11

C2H4

-actual number of atoms of each element in a molecule

Question 12

what is the structural formula (for ethene)

Answer 12

CH2CH2

-shows arrangement of atoms carbon by carbon

Question 13

what is a homologous series

Answer 13

-a group of compounds that can all be represented by the same general formula

Question 14

what is a functional group

Answer 14

• a group of atoms that determine how a compound typically reacts

Question 15

definition of isomer

Answer 15

two or more molecules with the same molecular formulae but different structural formula

Question 16

what can you infer from differently shaped carbon chains

Answer 16

• these isomers have similar chemical properties

- but different physical properties due to the change in shape of the molecules

Question 17

what could you infer from functional groups being in different places

Answer 17

-these isomers have different physical properties

Question 18

what could you infer from functional groups being different

Answer 18

-these isomers have different physical and chemical properties

Question 19

What is a hydrocarbon?

Answer 19

a compound of hydrogen and carbon only

Question 20

What happens when you burn a fuel?

Answer 20

releases energy in form of heat

Question 21

What is burning a fuel also known as?

Answer 21

-combustion reaction

Question 22

Why do hydrocarbons make great fuels?

Answer 22

as the combustion reaction that happens when you burn them in oxygen gives out lots of energy

Question 23

hydrocarbon + oxygen =

Answer 23

carbon dioxide + water

Question 24

What is complete combustion

Answer 24

-when you burn hydrocarbons in plenty of oxygen, the only products are CO2 and water

Question 25

What type of reaction is hydrogen + oxygen?

Answer 25

complete combustion

Question 26

What does incomplete combustion produce?

Answer 26

carbon monoxide + soot + carbon

Question 27

When does incomplete combustion occur?

Answer 27

when there is not enough oxygen around

Question 28

How is carbon monoxide is poisonous?

Answer 28

- It combines to red blood cells and stops blood doing proper job of carrying oxygen round the body - lack of oxygen in blood supply can result in death

Question 29

What is acid rain caused by?

Answer 29

- sulfur dioxide | - nitrogen oxides

Question 30

When may sulfur dioxide and nitrogen oxides be produced?

Answer 30

when fractions from crude oils are burned

Question 31

Where does sulfur dioxide come from?

Answer 31

comes from sulfur impurities in hydrocarbon fuel

Question 32

How are nitrogen oxides formed?

Answer 32

- when temp is high enough for nitrogen and oxygen react in the air - this often happens in car engines

Question 33

What is made when sulfur dioxide and nitrogen oxides mix with water vapour in the clouds?

Answer 33

- dilute sulfuric acid and nitric acid | - the rain that then falls from these clouds is known as acid rain

Question 34

Why is acid rain an issue?

Answer 34

- causes lakes to become acidic | - many plants and animals die as a result

Question 35

What are alkanes?

Answer 35

- saturated hydrocarbons - they are chains of carbon atoms surrounded by hydrogen atoms - single bonds between carbon atoms

Question 36

What is the general formula for alkanes?

Answer 36

CnH2n+2

Question 37

What are the names of the first five alkanes?

Answer 37

``` methane ethane propane butane pentane ```

Question 38

What do alkanes burn in?

Answer 38

complete combustion reactions

Question 39

Write the word equation for the burning of propane

Answer 39

propane + oxygen -> carbon dioxide + water

Question 40

What do alkanes react with and what is this called?

Answer 40

alkanes react with halogens to form haloalkanes

Question 41

What type of light is needed to make a haloalkane?

Answer 41

ultraviolet light

Question 42

What type of reaction is a haloalkane made in?

Answer 42

substitution reaction

Question 43

What is a substitution reaction?

Answer 43

hydrogen atom from alkane is substituted with chlorine or bromine

Question 44

Write the word equation for the reaction of bromine with an alkane (methane)

Answer 44

methane + bromine -> bromomethane + hydrogen bromide

Question 45

What are addition polymers made from?

Answer 45

-unsaturated monomers

Question 46

How is an addition polymer formed?

Answer 46

by joining up many small molecules called | monomers

Question 47

What are polymers?

Answer 47

A large molecule made when many small molecules (monomers) join together. Consists of many repeat units.

Question 48

What is addition polymerisation

Answer 48

When lots of unsaturated monomer molecules open up their carbon-carbon double bonds and join together to form polymer chains

Question 49

What are Monomers?

Answer 49

Molecules which can join up to form a polymer.

Question 50

What does ethene become in addition polymerisation? -how does its displayed formula change

Answer 50

poly(ethene)- (c2H4)n ``` ethene displayed formula: H H \ / C = C / \ H H ``` ---> pressure and a catalyst H H H H H H -C-C-C-C-C-C- H H H H H H poly(ethene)

Question 51

What does propene become in addition polymerisation? -how does its displayed formula change

Answer 51

poly(propene)- (C3H6)n ``` propene displayed formula: H H \ / C = C / \ H CH3 ``` ---> pressure and a catalyst H H (-C-C-) n H CH3 poly(propene)

Question 52

Why is it diffiuclt to get rid of addition polymers

Answer 52

- as most addition polymers are inert - they don't react easily - as the carbon-carbon bonds in the polymer are very strong and aren't easily broken - this means it takes a v long time for addition polymers to biodegrade - the burning of plastics also release toxic gases, so you can't get rid of addition polymers that way

Question 53

Name 2 ways why polymers are hard to get rid of

Answer 53

- it takes a long time for addition polymers to biodegrade | - you can't burn them either as that releases toxic gases

Question 54

What is condensation polymerisation

Answer 54

Polymerisation of monomers in which each time two monomers combine, a small molecule such as water or hydrogen chloride is removed (e.g. a dicarboxylic acid and a diol).