Developing fuels

Question 1

What does exothermic mean?

Answer 1

Energy transferred to the surroundings.
Bond making (-)

Question 2

What does endothermic mean?

Answer 2

Absorbs energy from surroundings.
Bond breaking (+)

Question 3

What is enthalpy change?

Answer 3

Energy to and from surroundings is measured as enthalpy change.

Question 4

formula for enthalpy change

Answer 4

Hproducts- Hreactants

Question 5

What are enthalpy changes measured in?

Answer 5

kilojoules per mole

Question 6

system

Answer 6

refers to the bonds in the reactants and products of the systen

Question 7

surroundings

Answer 7

the rest of the world eg air and test tube

Question 8

What are standard conditions?

Answer 8

To compare enthalpy changes standard conditions are chosen.

Question 9

What’s the standard temperature?

Answer 9

298k

Question 10

What is the standard pressure?

Answer 10

100 kPa

Question 11

What is the standard concentration of solutions?

Answer 11

1 mol/dm3

Question 12

How to convert Celsius to Kelvin?

Answer 12

Add 273

Question 13

Standard enthalpy change of a reaction

Answer 13

The enthalpy change when molar quantities of reactants react together under standard conditions.

Question 14

Standard enthalpy change of combustion

Answer 14

Enthalpy change that occurs when one mole of a substance is burnt in oxygen. Impossible under standard conditions.

Question 15

Standard enthalpy change of formation

Answer 15

Enthalpy change that occurs when one mole of a compound is formed from its elements. When you make one mole of water from hydrogen and oxygen , 286kj are transferred to surroundings.

Question 16

Enthalpy cycles (Hesse’s law)

Answer 16

Provide an alternative route to find the enthalpy change for a difficult to measure reaction.

Question 17

Aromatic compounds

Answer 17

If the carbon atoms contain a benzene ring they are called aromatic compounds (historical) and called arenes.

Question 18

Aliphatic compounds

Answer 18

They do not contain a benzene ring

Question 19

homologous series

Answer 19

methane, ethane, propane and butane as they all differ by CH2.

Question 20

General formula for alkanes

Answer 20

CnH2n+2

Question 21

Why are alkanes saturated?

Answer 21

They have single bonds

Question 22

What is the alkyl group?

Answer 22

the alkane with a hydrogen removed

Question 23

examples of alkyl groups

Answer 23

methyl (CH3)
ethyl (CH3 CH2)
propyl (CH3 CH2 CH2)

Question 24

How to name cycloalkanes?

Answer 24

1. Count the no of C’s in the cyclic structure and find the correct prefix
2. Add -ane to the end of the cyclo prefix.

Question 25

formula for overall energy change

Answer 25

energy from bond breaking - energy for bond making

Question 26

Why are alkenes unsaturated?

Answer 26

Has a double bond

Question 27

Heterogenous catalyst

Answer 27

At a diff state to species in reaction. Adsorbing molecules onto an active site on the surface of the catalyst. These increase the proximity of molecules and weaken the covalent bonds in the molecules allowing reactions to occur more easily. Faster rate of reaction.

Question 28

Ideal gas equation

Answer 28

Pressure x volume = amount of gas (moles) x gas constant (8.31) x temp

Question 29

Sigma bond

Answer 29

Single c-c bond electrons are arranged between atoms in an area of increased electron density

Question 30

Pi bond

Answer 30

C=C bond there’s 1 sigma and second is pi

Question 31

Moles of a gas

Answer 31

Volume/ 24

Question 32

Solid line

Answer 32

Bond is in plane of paper

Question 33

Wedged line

Answer 33

Bond comes out plane of paper

Question 34

Dotted line

Answer 34

Bond goes into plane of paper

Question 35

Overall enthalpy change

Answer 35

Energy to break bonds (+ve) + energy to make bonds (-ve)

Question 36

Hess law enthalpies of formation

Answer 36

Arrows point up from central product C.

Question 37

Hess law enthalpies of combustion

Answer 37

Arrows point down. Products always water and CO2.

Question 38

Catalyst poisoning

Answer 38

Impurities in a reaction may bind to a heterogenous catalysts surface and block reactants from being adsorbed.

Question 39

Thermal cracking

Answer 39

High temp and high pressure

Question 40

Catalytic cracking

Answer 40

Produces aromatic compounds with carbon rings. Lower temp w normal pressure but a catalyst used to compensate. Hydrocarbon vapour passed over the heated catalyst.

Question 41

Test for alkenes

Answer 41

Bromine water colour change from orange to colourless.

Question 42

Electrophiles

Answer 42

Electron acceptors.

Question 43

Electrophilic addition

Answer 43

Reaction mechanism that shows how electrophiles attack the double bond in alkenes. Carbocation forms. A carbon atom with only 3 ions making it pos ion.

Question 44

Alkenes undergo addition reactions with hydrogen to form alkanes. Conditions depend on catalyst used:

Answer 44

1. Nickel: high temp and pressure 2. Platinum: room temp and pressure

Question 45

Alkenes undergo addition reactions with catalysts to form alcohols

Answer 45

1. Sulphuric acid then add water 2. Steam, phosphoric acid, high temp and pressure

Question 46

Stereoisomers

Answer 46

Same structural formula but diff spatial arrangement of atoms and bonds

Question 47

E isomer

Answer 47

Hydrogen atoms are apart of

Question 48

Z isomer

Answer 48

Hydrogen atoms together on the same side.