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Higher Chemistry > Unit 3 > Flashcards

Unit 3 Flashcards

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1
Q

7 factors that influence the design of a chemical process

A
  • Cost of feedstock
  • Availability of feedstock
  • Sustainability of feedstock
  • Product Yield
  • Opportunities for recycling
  • Energy requirements
  • Marketability of by-products
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2
Q

Feedstock

A

A substance from which other chemicals can be produced

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3
Q

Role of nitrogen in feedstock

A

Used to produce ammonia

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4
Q

Importance of Ethanol

A

Used to make ester ethyl ethanoate

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5
Q

Information on the cost of feedstock (Cheap)

A

-Nitrogen is obtained from air, salts are obtained from sea water which is cheap and plentiful

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6
Q

Information of the availability of feedstock

A

Metal ores have to be mined and transported a long way, adding cost and environmental considerations

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7
Q

Sustainability of feedstock

A
  • How long a feedstock is likely to last

- If it’s a limited supply it can only be produced from one raw material, the cost will be high

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8
Q

Raw Materials

A

A naturally occurring substance that can be converted into feedstock

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9
Q

Important Raw Materials

A

Fossil fuels, metal ores, air and water, biomass (Animals and plant material)

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10
Q

High product yield

A

Allows more profit to be made

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11
Q

Opportunities for recycling

A

Recycling unreacted reactants saves money and reduced waste

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12
Q

Energy requirements

A
  • The heat produced during exothermic reactions can be used to heat reaction vessels and buildings which save money
  • Using a catalyst lowers the temperature and cost of heating
  • Endothermic reactions require heating which is costly
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13
Q

Marketability of by-products

A
  • Useful by-products are sold to increase profit

- Toxic by-products can be costly to dispose of safely

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14
Q

Environmental Considerations

A

Strict codes of conduct must be followed to ensure that chemicals and processes used have minimum impact on the environment

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15
Q

Three main environmental considerations

A
  • Minimising Waste
  • Avoiding use of production of toxic substances
  • Designing biodegradable products
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16
Q

GFM Triangle of Knowledge

A

m = n x GFM

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17
Q

Volume Triangle of Knowledge

A

n = c x v

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18
Q

How to change the volume if given in ml or cm3

A

Divide by 1000

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19
Q

Triangle of Knowledge for molar volume

A

v = n x Vmol

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20
Q

Atom Economy

A

(Mass of Desired Products / Total mass of reactants) x 100

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21
Q

Advantages of a higher AE

A

Lower the waste, more ‘green’, more efficiently expensive raw materials are used

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22
Q

Percentage Yield

A

(Actual Yield/Theoretical Yield) x 100

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23
Q

In PY, reasons why it wouldn’t be 100%

A
  • The product may be lost during purification

- The reaction may have side reactions which compete with the desired products

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24
Q

Displacement Reactions

A

An element higher up the electrochemical series displaces an element lower in the series from a solution of it’s ions

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25
Q

Reducing Agents

A
  • Allows other substances to get reduced

- The reducing agents gets oxidised and donates (lose) electrons

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26
Q

Oxidising Agents

A
  • Allows other substances to get oxidised

- The oxidising agent get reduced and accepts electrons

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27
Q

Rules for writing redox equations

A
  1. Identify the two reactants
  2. Start at the top of list on pg12 of your databook and work down till you come to reactant
  3. Continue down the list until next reactant
28
Q

The enthalpy of combustion

A

The energy released during the complete combustion of 1 mol of a substance

29
Q

The enthalpy of formation

A

The change in energy associated with the formation of 1mol of a compound from it’s elements in their standard states

30
Q

The enthalpy of solution

A

The energy change associated with dissolving 1mol of the solute in water

31
Q

Calculating the enthalpy of combustion

A
  1. Eh = mc ΔT
    2.The number of moles so, n=m/gfm OR n=c x v
  2. ΔH = Eh/n
    ‘+’if endothermic and ‘-‘ if exothermic
32
Q

Reasons why values of enthalpy might be different from the databook

A
  • Heat loss to it’s surroundings, a lower value of ΔT
  • Incomplete combustion of alcohol
  • Loss of alcohol through evaporation
33
Q

Calculating Hess’s Law (With Cycle)

A
  • Write target equation
  • Fit all the information needed for the calculation into a cycle
  • Solve the calculation by applying Hess’s Law
34
Q

Calculating Hess’s Law (With Equations)

A
  • Write out target equation
  • Write out the equation for the enthalpy change you are trying to find
  • Put a tick by each equation that is going in the right direction and change the sign of the enthalpy change if the equation needs to be reversed to fit the target equation
  • Apply Hess’s Law
35
Q

Hess’s Law

A

This states that the enthalpy change for a chemical reaction is independent of the route taken

36
Q

Molar bond enthalpy

A

The energy needed to break one mole of bonds to form separate atoms in the gaseous state

37
Q

Going to completion

A

The reactions only go in the forward direction and keep going until one of the reactions is used up

38
Q

Reversible Reaction

A

The products of the reaction can react/ decompose to reform the reactions

39
Q

Equation for the Haber Process

A

N2(g) + 3H2(g) ↔ 2NH3(g)

40
Q

Hydrated Cobalt Chloride

A

The crystals contain water molecules

41
Q

Chemical formula for Hydrated Cobalt Chloride

A

CoCl2.6H20

42
Q

What happens when hydrated cobalt chloride is heated (Colour Change)

A

Bright pink to blue

43
Q

What blue substance is formed when hydrated cobalt chloride is heated

A

Anhydrous Cobalt Chloride (CoCl2)

44
Q

Equation for hydrated cobalt chloride and anhydrous cobalt chloride

A

CoCl2.6H2O(s) ↔ CoCl2(aq) + 6H20(l)

45
Q

A reversible reaction has reached a state of equilibrium

A

The rate of the forward and reverse reaction become equal

46
Q

During equilibrium what happens to the concentration of reactants and products

A

They remain constant

47
Q

Are products and reactants equal concentration at equilibrium

A

No, they’re usually different

48
Q

Closed system at equilibrium

A

No reactants or products are added or removed, i.e. if it’s gases then they’re stopped from escaping

49
Q

The reversible equation of water

A

H20(l) ↔ H+(aq) + OH-(aq)

50
Q

Where does the equilibrium lie in the water equation and why?

A

It lies to the left as there’s a higher concentration of reactants to products

51
Q

Factors that affect equilibrium

A

Concentration, Temperature and Pressure

52
Q

Conclusion for increasing the reactant concentration

A

By increasing the reactant concentration it shifts the equilibrium to the right as the rate of the forward reaction increases to remove the reactant again

53
Q

Conclusion for increasing the product concentration

A

By decreasing the reactant concentration/ increasing the product concentration it shifts the equilibrium to the left as the rate of the reverse reaction increases to produce more reactant

54
Q

Halide Ions

A

F-, Cl-, Br-, I-

55
Q

What happens to the equilibrium in a rise in temperature

A

A rise in temperature will shift the equilibrium in the direction of the endothermic reaction to remove heat and make the temperature fall again

56
Q

What happens to the equilibrium when there’s a fall in temperature

A

A fall in temperature will shift the equilibrium in the direction of the exothermic reaction to produce more heat and make the temperature rise again

57
Q

What would be the reason(s) for pressure to change the position of the equilibrium

A
  • It involves gases

- There’s different numbers of moles in gaseous reactants(s) and products(s)

58
Q

Conclusion Marks for concluding pressure changes

A

Mark 1= State the position of the equilibrium

Mark 2= Discuss whether the rate of the forward reaction or the rate of the reverse reaction has increased

59
Q

How does a catalyst affect the equilibrium

A

It doesn’t alter the position of the equilibrium or the value of ΔH but it increases the rate at which the equilibrium is reached.

60
Q

In Chromatography, why is there differences in polarity and/or size of molecules

A

They’re exploited to separate the components within a mixture

61
Q

Retention Time

A

Depending on the type of chromatography in use, the identity of a component can be indicated either by the distance it’s travelled or by the time it takes to travel through the apparatus

62
Q

How can chromatography results be represented?

A

By showing an indication of the quantity of substance present on the y-axis and retention time on the x-axis.

63
Q

Volumetric Analysis

A

Using a solution of accurately known concentration in a quantative reaction to determine the concentration of another substance

64
Q

Standard Solution

A

A solution of accurately known solution

65
Q

The end-point

A

The point at which the reaction is just complete

66
Q

What does titration determine

A

The volume of reactant solution required to complete the reaction

67
Q

Indicator

A

A substance that changes colour at the end-point

Higher Chemistry (3 decks)

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