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Higher Chemistry > Unit 3 - Chemistry In Society > Flashcards

Unit 3 - Chemistry In Society Flashcards

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1
Q

How can you tell if a reactant is in excess

A

There is too much of the chemical and some is left over after the reaction

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2
Q

How can you tell if a reactant is a limiting reactant

A

The reactant is all used up after the reaction. The chemical reaction stops

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3
Q

How would you calculate the number of moles present

A
  • work out formula

- work out ration of ions

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4
Q

What is the molar volume

A

One mole of all gases, at the same temperature and pressure, have the same volume

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5
Q

How can volume be calculated using molar volume

A

V = n x MV

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6
Q

What is percentage yield

A

Measure to show how much of the limiting reactant has been turned into the desired product

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7
Q

What is atom economy

A

Percentage of reactants that get turned into useful products

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8
Q

What is a sign of the reaction being more effective

A

Higher atom economy

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9
Q

What remains constant at equilibrium

A

Concentrations of reactants and products

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10
Q

When is a reaction at equilibrium

A

When the rates of the forward and reverse reactions are equal

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11
Q

What are the three factors affecting equilibrium

A
  • concentration
  • temperature
  • pressure
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12
Q

What is Le Chatlelier’s principle

A

If a system at equilibrium is subjected to any change, the system will adjust itself to counteract the applied change

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13
Q

When the concentration of a reactant increases, in what direction does the equilibrium move

A

Moves to the right

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14
Q

When the concentration of a product increases, in what direction does the equilibrium move

A

Moves to the left

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15
Q

An increase in temperature will have what effect on the position of equilibrium

A

Moves in direction of endothermic reaction

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16
Q

A decrease in temperature will have what effect on the position of equilibrium

A

Moves in direction of exothermic reaction

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17
Q

When is a reaction endothermic

A

Enthalpy change = positive

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18
Q

When is a reaction exothermic

A

Enthalpy change = negative

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19
Q

Which side does the equilibrium move to when there is an increase in pressure

A

Moves to the side with less moles

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20
Q

Which side does the equilibrium move to when there is a decrease in pressure

A

Moves to side with more moles

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21
Q

What effect does adding a catalyst have on the position of equilibrium

A

No effect

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22
Q

What type of reaction takes in energy

A

Endothermic

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23
Q

Why might endothermic reactions be expensive to run

A

May incur costs to supply energy to the reaction

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24
Q

What type of reaction releases energy

A

Exothermic

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25
Q

What type of reaction may require the removal of heat to prevent temperatures rising

A

Exothermic reaction

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26
Q

What can be used to heat reactants instead of fuels or electricity

A

Heat generated from an exothermic reaction

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27
Q

What can be used to remove heat fro a reaction vessel

A

Water from rivers

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28
Q

Why is it important to control the temperatures of reactions

A

To prevent explosions

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29
Q

What is enthalpy of combustion

A

Energy released when one mole of substance burns completely in oxygen

30
Q

What measurements need to be taken when measuring enthalpy of combustion

A
  • volume of water
  • mass of spirit burner at start and end
  • initial and final temperature of water
31
Q

Why can the experiment used to find enthalpy of combustion using a spirit burner and a copper can be inaccurate

A
  • evaporation of alcohol
  • incomplete combustion
  • heat lost to surroundings
32
Q

What is Hess’s law

A

The enthalpy change for a chemical reaction is independent of the root taken

33
Q

Why is Hess’s law used

A

To determine enthalpy changes that cannot be measured directly

34
Q

What is bond enthalpy

A

The energy required to break one mole of a particular bond between a pair of atoms

35
Q

What is oxidation

A

The loss of electrons

36
Q

What is a reduction reaction

A

The gaining of electrons

37
Q

What is a redox reaction

A

Involves both an oxidation and a reduction reaction

38
Q

How can the overall redox reaction equation be found

A

Combining the ion electron equations for the oxidation and reduction then balancing the electrons to cancel

39
Q

What is an oxidising agent

A

A substance which accepts electrons

40
Q

What type of reaction does an oxidising agent take part in

A

Reduction reaction

41
Q

What is a reducing agent

A

Substance which donates electrons

42
Q

What type of reaction does a reducing agent take part in

A

Oxidation reaction

43
Q

What are some uses of oxidising agents

A
  • kill fungi, bacteria and inactive viruses

- breakdown of coloured compounds (used in bleach)

44
Q

In the electrochemical series which elements are more likely to be reducing agents and take part in oxidation reactions

A

Elements higher up in the series

45
Q

What are the elements lower down in the electrochemical series likely to be

A

Oxidising agents, taking part in reduction reactions

46
Q

How would you decide if a reaction is possible

A

Identify oxidation and reduction reactions then if the redox formed is the same as example then the reaction is possible

47
Q

What are the steps for balancing an ion electron equation

A
  • write equation
  • balance metals/non-metals
  • balance oxygens by adding H2O
  • balance hydrogens
  • balance charges
48
Q

What is a standard solution

A

Solution with an accurately known concentration

49
Q

What is volumetric analysis

A

Using a standard solution in a quantitative reaction to determine the concentration of another solution

50
Q

What type of experiment is used in volumetric analysis

A

Titration

51
Q

What must be done first before accurate readings are used

A

Rough titration

52
Q

Why is an indicator used

A

Used to find end point

53
Q

What could be used to achieve a precise end point.

A

White tile

54
Q

How is a standard solution made up

A
  • calculate mass of solid
  • weigh out mass into beaker
  • add water
  • pour into 1 litre flask
  • rinse beaker and add washings to flask
  • make up to mark with water
55
Q

Why is chromatography used

A

Used to separate and analyse mixtures

56
Q

In paper chromatography what is the mobile and stationary phases

A

Mobile - liquid solvent

Stationary - paper

57
Q

In thin-layer chromatography (TLC) what is the mobile and stationary phases

A

Mobile - liquid solvent

Stationary - silica on glass

58
Q

In gas-liquid chromatography what is the mobile and stationary phases

A

Mobile - gas

Stationary - liquid stuck to solid

59
Q

How does polarity affect paper chromatography

A

The less polar the substance the further it moves up, dissolves in solvents mobile phase

60
Q

If a molecule is more polar how does this affect the distance it travels

A

Moves less further up, dissolves in stationary phase

61
Q

What is used to reveal spots in thin-layer chromatography

A

A locating agent or UV light

62
Q

What type of chromatography produces a graph

A

Gas-liquid chromatography

63
Q

What does a a graph produced from gas-liquid chromatography show

A
  • number of compounds in mixture
  • how much of each compound present
  • retention time
64
Q

What is retention time affected by

A
  • size of molecule

- polarity of molecule

65
Q

How does the size of a molecule affect retention time

A

Larger molecule = longer retention time

66
Q

How does the polarity of a molecule affect retention time

A

More polar = longer retention time

67
Q

What is a raw material

A

Initial starting materials from which a processes feedstock is derived

68
Q

What is a feedstock

A

Reactant from which other chemicals can be extracted or synthesised

69
Q

How is a feedstock derived from a raw material

A

By physical separation or by chemical reaction

70
Q

What must raw materials and feedstocks be to maximise profits

A
  • readily available
  • from sustainable sources
  • suitable cost
71
Q

What other factors must be considered to maximise profits

A
  • recycling of materials
  • energy requirements minimised
  • by products sold
  • high yield and maximum atom economy
72
Q

What environmental considerations must be made when dealing with industrial chemical processes

A
  • minimise production of waste

- avoid use or production of toxic materials/ those that won’t degrade in environment

Higher Chemistry (3 decks)

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