paper 2 past paper questions Flashcards

1
Q

test for aldehydes and ketones and results

A

tollens reagent
- aldehyde: silver mirror
-ketone: no observation

or fehlings solution
aldehyde: orange/red precipitate
ketone: no observation

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2
Q

whats the meaning of fractions in fractional distillation

A

a mixture of compounds with similar boiling points

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3
Q

whats the catalyst used for catalytic cracking

A

zeolites

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4
Q

test for alkenes and alkanes and results

A

bromine water

-alkene: turns colourless
-alkanes: no observation

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5
Q

why does carbon dioxide absorb infrared radiation

A

the C=O bond vibrates at the frequency of IR radiation

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6
Q

what environmental problem does NO cause

A

acids rain

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7
Q

why may experimental and theoretical enthalpies differ

A

the value measured may not be accurate due to heat loss or incomplete combustion

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8
Q

What’s is a reflux reaction

A

heating the chemical reaction while continually cooling the vapour produced back into liquid form, using a condenser

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9
Q

How are oxides of nitrogen formed in engines

A

High temperatures in engines drive reactions between nitrogen compounds from the fuel and the oxygen

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10
Q

State the meaning of the term heterogeneous catalyst.

A

A catalyst that is in a different phase to the reaction

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11
Q

what happens in benzene

A

the p orbitals overlap
electrons are delocalised

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12
Q

why does using a conical flask instead of a beaker give more accurate results in some experiments

A

it reduces loss of liquid droplets and makes sure all the solution flows back into the bottom of the flask

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13
Q

why is chloroethanoic acid stronger acid than ethanoic acid

A

the chlorine atom polarises the O-H bond which weakens it making it a better proton donator

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14
Q

what reaction is responsible for the formation of nitro benzene from benzene

A

electrophilic substitution

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15
Q

reagents and conditions for prop-2-ene nitrile to 3-bromopropanenitrile

A
  • KCN
  • ethanolic
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16
Q

test for primary and secondary alchols

A
  • add potassium dichromate
  • gently warm
    *H2SO4
17
Q
  • whats the mistake in this test and what is it supposed to test for
  • add fehlings solution and cool in iced water
A
  • not supposed to cool instead you need to warm
  • it test for aldehydes and ketone
    • brick red for aldehydes
18
Q

what is one possible environmental problem with the complete combustion of biofuels made from sewage sludge

A

causes acid rain as SO2 is made

19
Q

what would methanol dissolve

A

methanol is a polar solvents so it will only dissolve polar molecules and non polar solvents dissolve non polar solvents

20
Q

what is a free radical

A

a molecule with an unpaired electron

21
Q

why would you add anydrous calcium chloride at the end of a ethyl enthanoate esterification reaction

A

its a drying agent so it will remove any water

22
Q

why might a reaction not have a 100% percentage yield

A
  • its a reversible reaction
  • side reactions
  • product lost during separation
23
Q

why are racemic mixtures formed

A

they have a planar shape so they can be attacked from either side with equal probability

24
Q

how is the strength for a base determined

A

the availability of its lone pairs, if its close to a electron withdrawing group the lone pairs are less available (benzene rings)
next to a positive inducing affect group (alkyls)

25
deduce the type of interaction that occurs between a lysine R group and an aspartic acid R group
ionic bonding
26
name the other substance formed when 2 amino acids react together to form part of a protein chain
water
27
what is the type of reaction between an ester and a hydroxide
hydrolysis
28
a triester in vegetable oil reacts with sodium hydroxide give one use of the product of the reaction
soap
29
when doing titrations why would using a smaller target titre wouldn't be appropriate
similar titre will increase uncertainty
30
what is a disadvantage of using a tripod and gauze when calculating enthalpy of combustion
tripod and gauze would reduce heat transfer
31
why is benzene more stable that kekules structure
because benzene has a ring of delocalised electrons
32
why do chemists design production methods with fewer steps
less energy used or better yeild
33
why do chemists design production methods with higher percentage atom economy
less waste or less pollution