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mistakes Flashcards

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1
Q

Why are lipase-cataylsted methods used over a base-catalysed reaction to produce biodiesel (4)

A

produces a higher yield as it does not produce the soaps that are
formed using a base-catalysed method

produces a higher purity biodiesel than when the base-catalysed
method is used

More environmentally friendly as lipases are biodegradeble while soaps are not

Lipase reactions are safer as they do not require the use of caustic materials such as sodium hydroxide, used in base reactions

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2
Q

Give a reason why when HCl is added to distilled water, a large pH change occurs

A

There is insignificant OH- to react with the added H3O+ ions so a pH change occurs

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3
Q

Similarities between pentane, pentanal and pentanoic acid

A

All have similar dispersion forces due to size/structure

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4
Q

What organic compound is an enzyme

A

Protein molecule

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5
Q

Benefits of using a cataylst

A
  • Increases rate of formation of desired product
  • Lowers operating temp and pressure
  • They are reusable making them cost effective
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6
Q

What are the 2 effects of increasing temperature on a reaction-time graph

A

Equilibrium is reached sooner
Starting Reaction rate is higher

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7
Q

Why is NaOH not a suitable primary standard (3)

A

Readily absorbs moisture
Readily reacts with CO2
Relatively lower degree of purity
Relatively low molar mass

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8
Q

Hydroscopic vs Deliquiscent

A

Hydroscopic absorbs water molecules from air
Deliquiscent absorbs water molecules from surrounding liquid

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9
Q

Do catalysts form an intermediate species

A

Yes (enzyme complex)

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10
Q

Observations -
Bromine water is added to potassium iodide solution, then dichloromethane is added as an organic solvent.

A

Orange solutions added to colourless solution which becomes brown. Then a colourless solution is added to a brown solution which remains as two layers with the bottom layer purple.

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11
Q

2 advantages of a fuel cell over a primary and secondary cell

A

Fuel Cells have a constant flow of reactants meaning they can operate as long as fuel is available

Fuel Cells produce a constant voltage

Fuel cells have a higher efficiency

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12
Q

Definition of a salt bridge/electrolyte and 3 purposes of it

A

Maintains electrical neutrality
- Allows anions to flow from the salt bridge to the anode and cations to flow from the salt bridge to the cathode
- Completes the electrical circuit

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13
Q

Why do soaps not function well in hard water

A

Ca2+ + CH3(CH2)16COO- ->
The surfactant ions form a precipiate known as scum which prevents soap from interacting with water, preventing cleaning action

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14
Q

Name functional group in glycerol

A

alcohol

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15
Q

What are the 2 distinctive part of the fatty acid used to make soap

A

Long hydrocarbon chain
Carboxyl group

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16
Q

Why are soap solutions basic

A

Carboxylate group accepts a proton making it basic
RCOO- + H2O ⇌ RCOOH + OH-

17
Q

Range of a titre

A

+-0.3ml

18
Q

What is the by-product of polymerisation

A

water

19
Q

Preferred metal for chemical tests?

A

Magnesium

20
Q

Random Error vs Systematic Error

A

Random errors are fluctuations in measured data due to limitations of the measurement device/technique, they occur unpredictably and to varying extents throughout the experiment. Non-directional effect on results.

Systematic errors are repeatable errors that occur due to faulty equipment
or poor experiment design, they occur consistently to the same extent
throughout the experiment. Results are skewed in one direction.

21
Q

Effect of smaller sample size on reliability

A

Decreases reliability as it increases the effect of random error

22
Q

How does a salt bridge work in terms of ion movement

A

Negative ions travel through the salt bridge and move (migrate) into
the anode half-cell
Due to an increase in positive ions/charge

Positive ions travel through the salt bridge and move (migrate) into
the cathode half-cell 1
Due to a removal of positive ions/charge

23
Q

What is the Leclanche cell an example of

A

Primary

24
Q

What is a sacrificial anode

A

A sacrificial anode is a piece of metal (that is connected to another metal)
that is more easily oxidised than the metal being protected from
corrosion

25
Q

Differences between Addition and Condensation Polymerisation

A

Condensation polymerisation produces small molecules such as water, addition does not.

Addition polymerisation involves the conversion of a C=C double bond
to a single bond, condensation does not.

Condensation polymerisation can result in the formation of, for
example, polyamides or polyesters, addition does not.

Condensation polymerisation involves the reaction of monomers withdifferent functional groups to form bonds in the polymer, addition does
not.

26
Q

Is H2PO4 acidic or basic

A

Acidic

27
Q

Is HCO3 acidic or basic

A

Basic

28
Q

Is HPO4 acidic or basic

A

Basic

29
Q

Tertiary Structure definition and explanation for formation

A
  • Interactions that occur between the side chains of the a-amino acids in the proteins
    • May be H-bonding, ionic bonding, dipole-dipole forces, covalent bonding or dispersion forces
    • Gives rise to the protein molecule folding (bending and twisting) in such a way to achieve max stability
30
Q

Conditions, Pressure and % Yield for Synthesis via Ethene

A
  • Temperature of around 300C and pressure of 6-7 MPa
  • Yield of 95%
31
Q

Explain how soap can clean greasy dishes

A
  • The strength of the dispersion forces between thenon-polartail of the soap molecule (or surfactant ion) and thenon-polargrease are strong enough to overcome the soap-soap dispersion forces and grease-grease dispersion forces
  • The strength of theion-dipole forcesbetween the anionic head and water are strong enough to overcome the soap-soap dispersion forces and water-water hydrogen bonding, dipole-dipole bonding and dispersion forces.
  • The soap molecule forms amicellewhich lifts the grease from the plate and allows it to forman emulsionin the water
    • Hot water and agitation further improve the cleaning action of soap
32
Q

Explain Properties and Uses of Polyethene

A

Low Density Polyethene
- Relatively low melting point, soft, flexible and insulating
- Used for packing film, tubing, bottles, toys

High Density Polyethene
- Relatively higher melting point, hard, rigid
- Used for chopping boards, pipes, toys and crates

33
Q

Explain Forces, Properties and Uses of Polytetrafluorothylene (PTFE)

A
  • High strength C-F bponds give it high chemical resistance, high electrical resistance, high melting point and is non-stick
  • Used for cooking pans, semi-permeable membranes in fuel cells and coatings on bearings
34
Q

Explain Forces, Properties and Uses of Polythylene Terephthalate (PET)

A
  • Dipole-Dipole forces give it a Strong, rigid and transperent properties
  • Thermal blankets, plastic bottles, fibres, solar cells
35
Q

Explain Forces, Properties and Uses of Nylon

A
  • Ability for hydrogen bonding between lone pair of electrons of oxygen in carbonyl group and hydrogen atom from amine group give it strong tensile strength, high melting point, high chemical resistance
  • Used in fishing lines, rope, carpet, parachutes, tents
36
Q

2 Examples of condensation polymers

A

Nylon
Polyethylene terephthalate (PET)

37
Q

2 Examples of addition polymers

A

Polyethene
Polytetrafluorothylene (PTFE)

38
Q

3 characteristics of zwitterions

A
  • Zwitterions have much higher melting points - because they possess ionic bonding
  • Dipolar nature of zwitterions also makes them very soluble in water - interacts through ion-dipole interactions
  • Dipolar nature of zwitterions allows them to act as acids or bases and can also act as buffers

chem again (7 decks)

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