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Higher Chemistry > Unit 3 > Flashcards

Unit 3 Flashcards

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1
Q

What are the two triangles used for calculations based on balanced equations

A

/\
/M\
——-
/N | gfm\

   /\
 / n\   ------- /c    | v  \
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2
Q

What is a limiting factor

A

During a chemical reaction, product is continually formed until one of the reactants is completely used up

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3
Q

How do you calculate the molar volume

A

Density= mass

Volume

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4
Q

What is the average molar volume of a gas At standard temperature and pressure

A

22.4l

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5
Q

Solids liquids and solutions are considered to……..when compared paired with gases

A

Have no volume

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6
Q

What does dynamic equilibrium mean for the product yield?

A

We do not get 100% product

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7
Q

What is the formula for percentage yield?

A

Py=Ay

Ty X100

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8
Q

What is theoretical yield

A

The expected mass produced from a known mass of reactant, which is calculated from a balanced equation

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9
Q

What is actual

A

The mass of desired product obtained which is less than the theoretical yield

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10
Q

The actual yield is less than the theoretical yield because…

A

The reaction hasn’t gone to completion i.e dynamic equilibrium
Other reactions are occurring that that compete with the desired reaction
Separation of desired products is difficult (i.e distillation)
The product maybe impure or lost during purification
Industrial processes require a high yield and high purity of products, therefore, unreacted reactants are recycling

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11
Q

Describe percentage yeild

A

Gives us information relative to the amount (%) of reactants that have successfully converted into products (During dynamic dynamic equilibrium reactions) it does not give information regarding by products formed

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12
Q

What can make by products costly to deal with?

A 
If they are 
-Toxic 
-Corrosive 
-Flammable 
I.e by products harmful to the environment
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13
Q

What makes a reaction most desirable (in an Atom Economy sense)

A

Reactions in which most of the reactant atoms are converted into products

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14
Q

What is the formula for Atom Economy?

A

Total mass
of desired product
Atom Economy= __________
Total mass of
All reactants

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15
Q

A reversible reaction is…

A

One that proceeds in both the forward and reverse direction

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16
Q

Reversible reactions reach a state of dynamic equilibrium when…

A

the rate of the forward reaction is exactly equal to the rate of the reverse reaction

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17
Q

At dynamic equilibrium there is NOT 50% reactants and 50% products however….

A

The concentrations of the reactants and products was constant at dynamic equilibrium

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18
Q

Name the three ways the dynamic equilibrium can be changed

A

Concentration
Pressure
Temperature

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19
Q

What is the Le chatelier’s principle

A

If a system at equilibrium is subject to any change, the system readjusts itself to counteract the applied change

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20
Q

Consider the following reaction

A+B 🔁C+D

What would happen if you increased the concentration of A or B

A

According to le chateliers principle

The system will decrease the concentration of A or B

By promoting the forward reaction

Moving the equilibrium to the right producing more product (ie C+D)

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21
Q

Consider the following reaction

A+B 🔁C+D

What would happen if you decreased the concentration of C or D

A

According to le chateliers principle

The system will increase the concentration of C or D

By promoting the forward reaction

Moving the equilibrium to the right producing more product (ie C+D)

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22
Q

Consider the following reaction

A+B 🔁C+D

What would happen if you decreased the concentration of A or B

A

According to le chateliers principle

The system will increase the concentration of A or B

By promoting the reverse reaction

Moving the equilibrium to the left producing more reactants(ie C+D)

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23
Q

Consider the following reaction

A+B 🔁C+D

What would happen if you increased the concentration of C or D

A

According to le chateliers principle

The system will decrease the concentration of C or D

By promoting the reverse reaction

Moving the equilibrium to the left producing more reactants (ie A+B)

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24
Q

The effects of changing pressure on a system involving gasses is equivalent to ….

A

The effects of changing concentration

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25
Q

Consider the following reaction

3A(g)+B(g) 🔁2C(g)

What would be the effect of increased pressure?

A

According to le chateliers principle

The system will decrease the pressure

By promoting the forward reaction

Moving the equilibrium to the right producing more products

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26
Q

Consider the following reaction

3A(g)+B(g) 🔁2C(g)

What would be the effect of decreased pressure?

A

According to le chateliers principle

The system will increase the pressure

By promoting the reverse reaction

Moving the equilibrium to the left producing less products

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27
Q

Pressure has no effect when both the reactants and products….

A

Occupy the same volume

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28
Q

Consider the following reaction

 3A(g)+B(g) 🔁2C(g)
      ↗️                      ↖️ Exothermic                  Endothermic

What would be the effect of decreased temperature ?

A

According to le chateliers principle

The system will increase the temperature

By promoting the forward reaction

Moving the equilibrium to the right producing more products

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29
Q

Consider the following reaction

 3A(g)+B(g) 🔁2C(g)
      ↗️                      ↖️ Exothermic                  Endothermic

What would be the effect of increased temperature ?

A

According to le chateliers principle

The system will increase the temperature

By promoting the reverse reaction

Moving the equilibrium to the left producing less products

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30
Q

A catalyst does not…

A

change the equilibrium position

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31
Q

A catalyst…

A

Speeds up the rate of reaction of a chemical reaction by providing an alternative reaction pathway with a lower activation energy

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32
Q

In a reverse reaction catalyst lowers the activation energy

A

For both the forward and reverse reaction

As a result the reaction reaches a dynamic equilibrium faster

33
Q

Enthalpy of combustion

A

Enthalpy of combustion of a substance is the enthalpy change when ONE MOLE OF FUEL is completely combusted

34
Q

Enthalpy of solution

A

The enthalpy change of solution is the enthalpy change when ONE MOLE OF THE SOLUTE (solid) is completely dissolved in water

35
Q

Enthalpy of neutralisation

A

The enthalpy change of neutralisation is enthalpy change when ON MOLE OF WATER is formed

36
Q

What is step 1 in calculating the enthalpy of combustion

A

Eh=cm🔼T

37
Q

What is step 2 in calculating the enthalpy of combustion

A

n= M
—–
GFM

38
Q

What is step 3 in calculating the enthalpy of combustion

A

🔼H= Eh
——
n

39
Q

What does a black deposit of carbon indicate in an enthalpy of combustion reaction

A

Incomplete combustion

40
Q

What can incomplete combustion be counteracted with

A

Bomb calirimeter

41
Q

What can prevent heat being lost to the surroundings

A

Heat shield

42
Q

What increases the accuracy of an experiment

A

Reputation

43
Q

What is hess’s law?

A

States that the enthalpy change of a chemical reaction depends only on the chemical nature and physical state of reactants and products and is independent of any intermediate steps

44
Q

Enthalpy of combustion

A

The amount of energy released when 1 mole of a fule is completely burnt in oxygen

45
Q

Enthalpy of formation

A

The energy required to form one mole of a substance from its elements in their natural state

46
Q

What was the average growth of the chemical industry between 1995 and 2000

A

5 times that of all other manufacturing industries

47
Q

industrial process are designed to…

A

Maximise profit and minimise their impact on the environment

48
Q

Feedstock

A

A reactant from which other chemicals can be extracted or synthesised to manufacture a required product

49
Q

Raw material

A

The original source of feedstock

50
Q

What are the major raw materials?

A

Crude oil
Metallic ores and minerals
Air
Water

51
Q

What are the factors that myst be taken into account when choosing a manufacturing rout

A 
Cost, availability and sustainability of feedstock 
Yield of product
Recyclability of unreacted materials
Marketability of by-products
Difficulty and cost of wast disposal
Energy consumption 
Atmospheric emissions
52
Q

What are the environmental factors that must be taken into account when choosing a manufacturing rout

A

Minimising waste
Avoiding the use or production of toxic substances
Design products that will biodegrade if appropriate

53
Q

How do manufacturing plants save energy?

A

Switch to processes requiring less energy
Utilise the heat from exothermic reaction elsewhere
Use waste heat to generate energy
Sell exess energy to supply heating for local housing

54
Q

REDOX reactions

A

Reduction and oxidation reaction are occurring simultaneously

55
Q

If magnesium is loosing e- there for it is being…

A

Oxidiesed

56
Q

Metals higher in the ECS ..

A

Displace metals lower in the electrochemical series from a solution of its ions

57
Q

Electronegativity indicates

A

Whether an element will act as an oxidising or reducing agent

58
Q

Most non metal elements act as…

A

Oxidising agents

59
Q

Metals have low electronegativities hence

A

Act as reducing agents

60
Q

Oxyanon ions are

A

Negative ions that contain oxygen combined with other elements

61
Q

Examples of oxyanion ions

A

Sulphate ion- SO3^2-

Permanganate ion - MnO4^-

Dichromate ion- CrO7^2-

62
Q

What is step 1 of calculating the ion equation of redox reactions involving oxyanions

A

Add H2O to the left to balance the number of oxygen

63
Q

What is step 2 of calculating the ion equation of redox reactions involving oxyanions

A

Add appropriate number of H+(aq) ions to the right to balance H

64
Q

How do you calculate a REDOX reaction

A

Add the Redox and Oxidation ion electron equations together to form the REDOX equation
The number of electrons in each equation must be the same

65
Q

Describe chromatography

A

A small sample of a mixture is placed at the bottom of the chromatography paper and the paper is placed in a suitable solvent
The solvent moves up the chromatography paper by capillary action

66
Q

Why does separation occur in chromatography

A

The molecules in the mixture have different polarities and/ or masses

67
Q

Describe how polarity works in the context of chromatography

A

Polar solvents dissolve (bond to) polar molecules and carry them further up the chromatography paper than they do non-polar molecules

68
Q

Describe how mass works in the context of chromatography

A

The lighter a molecule the further it travels

69
Q

How do you identify amino acids by chromatography

A

Hydrolysed amino acids can be identified by chromatography. The hydrolysed amino acids are chromatographed against known amino acids
This process is repeated until all the amino acids in the hydrolysed olysed sample are identified

70
Q

What is an RF value?

A

It is common to measure the distance the sample has traveled and compare it with the distance the solvent has traveled, thus calculating a value known as the RF value
RF values are specific for individual molecules in specific solvents

71
Q

Formula for RF value

A

X
RF=—-
Y

72
Q

What is the mobile phase of gas liquid chromatography

A

An inert gas (ie doesn’t react) like N2 or Ne

73
Q

What is the stationary phase of gas liquid chromatography

A

A high boiling point liquid absorbed onto an inert solid that is placed in a long colum

74
Q

In gas liquid chromatography, each peak represents…

A

A compound in the mixture

75
Q

In gas liquid chromatography, the area under the peak is an indication of

A

the abundance of this compound in the mixture

76
Q

What is the stationary phase of paper chromatography

A

The net chromatography paper

77
Q

What is the mobile phase of paper chromatography

A

The solvent

78
Q

Name other forms of chromatography

A

TLC- Thin layer chromatography
GLS- Gas liquid chromatography
HPLC- high performance liquid chromatography
All identify components in the mixture and the abundance of each compound

Higher Chemistry (4 decks)

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