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Chemistry > Developing Fuels > Flashcards

Developing Fuels Flashcards

1
Q

What is the ideal gas equation?

A

pV=nRT

Pressure x volume = moles x 8.314 x temp K

Pa x m^3 = moles x J/K/mol x K

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2
Q

What volume of gas does 1 mole of a substance take up?

A

24dm^3 at room temp and pressure

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3
Q

How do you convert cm^3 to dm^3

A

divide by 1000

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4
Q

How do you convert dm^3 to m^3

A

divide by 1000

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5
Q

In the ideal gas equation what is volume measured in?

A

m^3

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6
Q

In the ideal gas equation what is temperature measured in?

A

Kelvin

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7
Q

How do you convert Celsius to Kelvin

A

Add 273

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8
Q

What can you use to measure gas produced by a reaction?

A

A gas syringe

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9
Q

In chemistry what is room temperature and pressure?

A

298 K (25 Celcius) 100KPa

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10
Q

Whats the equation for volume of gas at RTP

A

Moles = (volume in dm^3) / 24

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11
Q

What causes a change in enthalpy in a reaction?

A

bonds being made and broken

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12
Q

What are the standard conditions

A

298K and 100KPa

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13
Q

What are the four main stages of heterogeneous catalysis

A

Stage 1: adsorption to catalyst
Stage 2: reactants bonds break
Stage 3: New bonds made
Stage 4: Loss of product from catalyst surface

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14
Q

When calculating enthalpy changes do you pay attention to moles in the reaction

A

Yes - times by average bond enthalpy

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15
Q

What is standard enthalpy change of reaction?

A

Enthalpy change when reaction occurs in the molar quantities shown in chemical reaction
under standard conditions

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16
Q

What is the standard enthalpy change of formation?

A

enthalpy change when 1 mole of a compound is formed from its elements in standard states under standard conditions

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17
Q

What is standard enthalpy change of combustion

A

enthalpy change when 1 mole of a substance is completely burnt in oxygen under standard conditions

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18
Q

How do you calculate enthalpy change of reaction

A

(Energy absorbed to break bonds) - (Total energy released in making bonds)

Using average bond enthalpies

19
Q

What states must compounds be in when bond enthalpies are measured?

A

gas

20
Q

What do you do to work out number of molecules?

A

work out moles and times by avogadro’s constant

21
Q

What is an exothermic reaction?

A

A reaction which gives out energy

22
Q

What does a shorter bond length mean?

A

Means a stronger attraction and higher bond enthalpy

23
Q

What is average bond enthalpy?

A

the energy need to break one mole of bonds in the gas phase

averaged over many different compounds (explains why it’s not exact)

24
Q

What is bond length?

A

Distance between two positive nuclei repelling and the attraction of electrons balanced

25
Q

What are bond enthalpies measured in?

A

KJ/mol

26
Q

Is bond breaking exothermic or endothermic?

A

endothermic

27
Q

Is bond making exothermic or endothermic

A

exothermic

28
Q

What is an endothermic reaction?

A

absorbs energy - temp decreases

29
Q

What is Hess’s law?

A

The total enthalpy change of a reaction is always the same no matter what route is taken

30
Q

Do moles matter when calculating enthalpy changes using Hess’s cycles and standard enthalpies?

A

Yes (times amount of moles of product by enthalpy change for it)

31
Q

What does an enthalpy level diagram look like for an endothermic reaction?

A

products higher than reactants

32
Q

what does an enthalpy level diagram look like for an exothermic reaction?

A

reactants higher than products

33
Q

What’s different about an enthalpy level diagram with a catalyst?

A

It has two bumps

34
Q

What is activation energy?

A

minimum amount of energy needed to begin breaking bonds and start a chemical reaction

35
Q

What does less enthalpy mean for a substance?

A

more stable

36
Q

What is the equation for enthalpy changes?

A 
q = mcΔT
q= heat change
m= mass of water or solution
37
Q

What is standard enthalpy change of neutralisation?

A

Enthalpy change when an acid and alkali react to form 1 mole of water

38
Q

Why is the enthalpy of combustion in a lab likely to be a lower value then in a data book?

A

not done in standard conditions

39
Q

In q=mcΔT does it matter if T is kelvin or celsius?

A

no

40
Q

What is a catalyst?

A

Increases the rate of reaction by providing an alternative reaction pathway with a lower activation energy
The catalyst is chemically unchanged at the end of the reaction

41
Q

What catalyst is used in the haber process?

A

iron
Fe
N2 + 3H2 –> 2NH3

42
Q

What is used to test for alkene products?

A

bromine water

43
Q

why are catalysts used in cracking?

A

without one it requires high temp and pressure making it expensive

44
Q

How are catalysts used in cracking

A

Hydrocarbon vapour over heated solid catalyst

Chemistry (8 decks)

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