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Developing fuels Flashcards

(47 cards)

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1
Q

What is an endothermic reaction?

A

Heat energy transferred from the surroundings to the products, temperature of surroundings decreases

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2
Q

What is an exothermic reaction?

A

Heat energy transferred from reactants to surroundings, temperature of surroundings goes up

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3
Q

draw the reaction profiles of an endo and exothermic reaction

A

exothermic
reactants line higher up
products lower down with the activation energy labelled correctly, endothermic the other way around, reactants lower than the products.

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4
Q

What is enthalpy change?

A

Heat energy change per mole of substance, measured in KJ mol-1

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5
Q

What is standard conditions?

A

Specified temperature of 298K and 25 degrees celcius
pressure of 1 atmosphere
concentration of 1 mol/dm-3
delta H 298 with a circle around an O

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6
Q

What is the standard enthalpy change of combustion?

A

enthalpy change where one mole of a substance is burned completely in oxygen, under standard conditions

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7
Q

What is the standard enthalpy change of formation?

A

Enthalpy change where one mole of a substance is formed from its elements, with both the substance and the element being in their standard states

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8
Q

What is standard enthalpy change of neutralisation?

A

The enthalpy change when one mole of hydrogen ions react with one mole of hydroxide ions to form one mole of water under standard conditions

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9
Q

What is standard enthalpy change of reaction

A

The enthalpy change where one mole of quantities of reactants as stated in an equation react together under standard conditions

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10
Q

How does the enthalpy change of combustion practical work

A
  1. set up apparatus
  2. Add fixed volume of water to the calorimeter
  3. measure the mass of the burner
  4. measure the temperature of water
  5. light wick
  6. heat water, stir continuously
  7. extinguish burner using lid
  8. measure end temperature
  9. water
  10. re measure the mass of burner
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11
Q

what is enthalpy?

A

heat energy transferred per mole of substance at a constant pressure

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12
Q

calculation of enthalpy

A

E = MC delta T
divide answer by the number of moles per fuel burned

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13
Q

limitations of enthalpy change of combustion

A

energy transferred to surroundings
incomplete combustion
evaporation of fuel from wick

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14
Q

What is Hess’s law

A

The enthalpy change of any chemical reaction is independent from the intermediate stages, so long as the initial and final conditions are the same for each route

enthalpy change the same no matter what route taken

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15
Q

Enthalpy change of reaction PAG

A
  1. set up apparatus
  2. Use a pipette to add fixed volume of known concentration of solution to a polystyrene cup
  3. Measure mass of solid
  4. Measure start temperature
  5. Add solid
  6. Record maximum temperature reached by solution
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16
Q

Uncertainties

A

burette - 0.05
glass pipette - 0.06
volumetric flask - 0.2
thermometer - 0.5

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17
Q

What is a bond enthalpy?

A

Chemical Bond, sharing a pair of electrons leads to attraction between atoms, energy needed to break one mole of bonds in the gaseous state to give separate atoms

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18
Q

Bond breaking is?

A

endothermic

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19
Q

Bond making is?

20
Q

General formula of an alkane

21
Q

How does fractional distillation work?

Study These Flashcards
A
  1. crude oil oil heated -> gaseous
  2. Gas enters the fractioning column, heat rises then is cold
  3. Hydrocarbon molecules rise up the column and start to cool down
  4. Biggest molecules rise then condense to a liquid lower down due to their higher boiling points.
  5. Smallest molecules have lower boiling points and condense to a liquid higher up in the column
22
Q

Cycloalkanes general formula

23
Q

Aromatic ?

Study These Flashcards
A

Has a benzene ring

24
Q

Aliphatic ?

Study These Flashcards
A

Has no benzene ring

25
What is a functional group?
Modifiers responsible for characteristic chemical reactions of molecules
26
Complete combustion definition?
Hydrocarbon fuels reacting with oxygen in the air when they burn with lots of oxygen Gives out a lot of energy, only produces CO2 and H2O
27
Complete combustion equation
Hydrocarbon fuel + O2 -> CO2 + H2O
28
Incomplete combustion definition?
Not enough oxygen when a hcf is burnt produces CO and Soot
29
Incomplete combustion equation
Hydrocarbon fuel + O2 -> CO + H2O
30
What is found in crude oil?????????
methane, butane, ethane, propane, methylbutane, cyclohexane
31
Cracking definition
Using heat to break down larger molecules into smaller more useful molecules Any reaction in which a larger molecule is made into smaller molecules -> saturated and unsaturated
32
Catalytic Cracking
Heated in the presence of a catalyst, usually a zeolite, large porus 3D structure made of aluminium, silicon and oxygen atoms
33
What is a heterogeneous catalyst
Reactants and catalysts in a different state to eachother
34
Heterogeneous catalysis
1, Reactant molecules adsorb onto catalysts surface 2. Bonds within the reactants weaken and break 4. New bonds within the products form 5. Products desorb from catalysts surface
35
Catalyst poison
Stronger adsorption, blocks the active site on the catalysts surface.
36
Alkene general formula
CnH2n
37
Alkenes
contain at least on c=c making it unsaturated, held together by covalent bonds
38
Bromine tests for alkene
Bromine water turns orange to colourless Bromine liquid red/brown to colourless
39
Bromine tests for alkane
Bromine water stays orange bromine liquid stays red/brown
40
What is an electrophile?
Positive ion attracted to a region of negative charge, accepting a pair of electrons to form a covalent bond
41
What is a Carbocation?
Molecular ion containing a positive carbon atom
42
What is addition polymerisation?
Chemical reaction in which unsaturated monomers (small molecules) join together by addition reactions to produce a polymer (long molecule).
43
Bond angles of atoms
Line bond in the plane of the paper dash behind the plane of the paper wedge forwards, towards the plane of the paper alkanes -> always 109,5 because regions of electron density around the central carbon atom repel as far as possible Alkenes -> always 120 because three regions of electron density around the central carbon atom
44
Isomers
same formula, different atom arrangement
45
Structural isomers
Same formula, different atom bonding types chain Position Functional
46
Stereoisomers
Same molecular formulae atoms bonded together in the same order, arrangement different in each isomer
47
E/Z isomerism
Lack of free rotation around the central carbon atom bond

Chemistry (2 decks)

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