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Chemistry Y12 > Developing Fuels(DF) > Flashcards

Developing Fuels(DF) Flashcards

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1
Q

What is an exothermic reaction?

A

A reaction that releases energy/heat to the surroundings, causing the temperature of the surroundings to increase

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2
Q

In an exothermic reaction does the products or reactants have more energy?

A

Reactants

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3
Q

What happens to the difference in energy between reactants and products in an exothermic reaction?

A

The difference is release to the surroundings

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4
Q

What is an endothermic reaction?

A

A reaction that takes in heat/energy from the surroundings, causing the temperature of the surroundings to decrease

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5
Q

In an endothermic reaction does the products or reactants have more energy?

A

Products

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6
Q

What is activation energy?

A

The miniumum amount of energy that particles must have to react

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7
Q

What is a catalyst?

A

A catalyst is something which increases the rate of reaction, by providing an alternative pathway for the reaction with a lower activation energy, without being used up

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8
Q

Why are catalysts not involved in the chemical equation for a reaction?

A

They are not used up during the reaction

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9
Q

What are the benefits of using a catalyst?

A

-Allows a reaction to happen at a lower temperature=saves energy
-Saves money

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10
Q

What is enthalpy ΔH ?

A

The measure of heat energy in a system

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11
Q

How can you calculate enthalpy change?

A

ΔH =H products- H reactants

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12
Q

What is enthalpy change measure in?

A

kJ mol-1

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13
Q

For an exothermic reaction will the enthalpy change be positive or negative?

A

Negative

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14
Q

For an endothermic reaction will the enthalpy change be positive or negative?

A

Positive

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15
Q

What is the equation that links energy released, mass, specific heat capacity and temperature change?

A

Q = mc∆T

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16
Q

Does breaking bonds release or take in energy?

A

Takes in energy

17
Q

Does making bonds release or take in energy?

A

Releases energy

18
Q

What happens as bond length decreases?

A

The bond becomes stronger

19
Q

Why might calculated bond energy value differ from the figure provided?

A

-Bond energies are average values from several compounds=not always precise
-Bond energies assume all molecules are in a gaseous state

20
Q

If the energy needed to break the bonds is greater than the energy released when the new bonds are made is the reaction endo or exothermic?

A

Endothermic

21
Q

If the energy needed to break the bonds is less than the energy released when new bonds are made the reaction is the reaction endo or exothermic?

A

Exothermic

22
Q

Describe how to calcuale the enthalpy change of solution?

A
  1. Place known volume of water into a polystyrene beaker
    2.Add known mass of the other compund to the water and stir
    3.Measure temperature of water before and after
23
Q

Can atoms rotate freely around a single or double bond?

A

Single bond, in a double bond there is restricted rotation

24
Q

What are stereoisomers?

A

Molecules with the same structural formula but the atoms have a different spacial arrangment

25
Q

What are the two types of stereoisomers?

A

E and Z

26
Q

What is Z isomerism?

A

When the two highest-priority substituents are on the same side of the double bond axis

27
Q

What is E isomerism?

A

When the two highest-priority substituents are on opposite sides of the double bond axis

28
Q

What is cis-trans isomerism?

A

Alkenes with exactly two substituents on the double bond - with one on each carbon

29
Q

What is cis isomerism?

A

When the substituents are on the same side of the carbon double bond

30
Q

What is trans isomerism?

A

When the substituents are on different sides of the carbon double bond

31
Q

What direction do the arrows point for enthalpy changes and what is the equation?

A
  • Combustion=inwards
  • H1=H2-H3
  • Formation=outwards
  • H1=H3-H2

Formation=natural state of elements

32
Q

What is the standard enthalpy change of combustion?

A

The enthalpy change that occurs when mole of a substance is burnt completely in oxygen under standard conditons

33
Q

What does aromatic,aliphatic and arene mean?

A
  • Aromatic=contains a benzene ring
  • Aliphatic=does not contain a benze ring
  • Arene=hydrocarbon containing a benzene ring

Chemistry Y12 (6 decks)

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