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chemistry > Developing fuels > Flashcards

Developing fuels Flashcards

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1
Q

What does exothermic mean?

A

Energy transferred to the surroundings.
Bond making (-)

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2
Q

What does endothermic mean?

A

Absorbs energy from surroundings.
Bond breaking (+)

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3
Q

What is enthalpy change?

A

Energy to and from surroundings is measured as enthalpy change.

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4
Q

formula for enthalpy change

A

Hproducts- Hreactants

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5
Q

What are enthalpy changes measured in?

A

kilojoules per mole

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6
Q

system

A

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

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7
Q

surroundings

A

the rest of the world eg air and test tube

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8
Q

What are standard conditions?

A

To compare enthalpy changes standard conditions are chosen.

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9
Q

What’s the standard temperature?

A

298k

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10
Q

What is the standard pressure?

A

100 kPa

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11
Q

What is the standard concentration of solutions?

A

1 mol/dm3

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12
Q

How to convert Celsius to Kelvin?

A

Add 273

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13
Q

Standard enthalpy change of a reaction

A

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

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14
Q

Standard enthalpy change of combustion

A

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

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15
Q

Standard enthalpy change of formation

A

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.

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16
Q

Enthalpy cycles (Hesse’s law)

A

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

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17
Q

Aromatic compounds

A

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

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18
Q

Aliphatic compounds

A

They do not contain a benzene ring

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19
Q

homologous series

A

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

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20
Q

General formula for alkanes

A

CnH2n+2

21
Q

Why are alkanes saturated?

A

They have single bonds

22
Q

What is the alkyl group?

A

the alkane with a hydrogen removed

23
Q

examples of alkyl groups

A

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

24
Q

How to name cycloalkanes?

A
  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.
25
Q

formula for overall energy change

A

energy from bond breaking - energy for bond making

26
Q

Why are alkenes unsaturated?

A

Has a double bond

27
Q

Heterogenous catalyst

A

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.

28
Q

Ideal gas equation

A

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

29
Q

Sigma bond

A

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

30
Q

Pi bond

A

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

31
Q

Moles of a gas

A

Volume/ 24

32
Q

Solid line

A

Bond is in plane of paper

33
Q

Wedged line

A

Bond comes out plane of paper

34
Q

Dotted line

A

Bond goes into plane of paper

35
Q

Overall enthalpy change

A

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

36
Q

Hess law enthalpies of formation

A

Arrows point up from central product C.

37
Q

Hess law enthalpies of combustion

A

Arrows point down. Products always water and CO2.

38
Q

Catalyst poisoning

A

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

39
Q

Thermal cracking

A

High temp and high pressure

40
Q

Catalytic cracking

A

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

41
Q

Test for alkenes

A

Bromine water colour change from orange to colourless.

42
Q

Electrophiles

A

Electron acceptors.

43
Q

Electrophilic addition

A

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.

44
Q

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

A
  1. Nickel: high temp and pressure
  2. Platinum: room temp and pressure
45
Q

Alkenes undergo addition reactions with catalysts to form alcohols

A
  1. Sulphuric acid then add water
  2. Steam, phosphoric acid, high temp and pressure
46
Q

Stereoisomers

A

Same structural formula but diff spatial arrangement of atoms and bonds

47
Q

E isomer

A

Hydrogen atoms are apart of

48
Q

Z isomer

A

Hydrogen atoms together on the same side.

chemistry (7 decks)

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