paper 2 past paper questions Flashcards
test for aldehydes and ketones and results
tollens reagent
- aldehyde: silver mirror
-ketone: no observation
or fehlings solution
aldehyde: orange/red precipitate
ketone: no observation
whats the meaning of fractions in fractional distillation
a mixture of compounds with similar boiling points
whats the catalyst used for catalytic cracking
zeolites
test for alkenes and alkanes and results
bromine water
-alkene: turns colourless
-alkanes: no observation
why does carbon dioxide absorb infrared radiation
the C=O bond vibrates at the frequency of IR radiation
what environmental problem does NO cause
acids rain
why may experimental and theoretical enthalpies differ
the value measured may not be accurate due to heat loss or incomplete combustion
What’s is a reflux reaction
heating the chemical reaction while continually cooling the vapour produced back into liquid form, using a condenser
How are oxides of nitrogen formed in engines
High temperatures in engines drive reactions between nitrogen compounds from the fuel and the oxygen
State the meaning of the term heterogeneous catalyst.
A catalyst that is in a different phase to the reaction
what happens in benzene
the p orbitals overlap
electrons are delocalised
why does using a conical flask instead of a beaker give more accurate results in some experiments
it reduces loss of liquid droplets and makes sure all the solution flows back into the bottom of the flask
why is chloroethanoic acid stronger acid than ethanoic acid
the chlorine atom polarises the O-H bond which weakens it making it a better proton donator
what reaction is responsible for the formation of nitro benzene from benzene
electrophilic substitution
reagents and conditions for prop-2-ene nitrile to 3-bromopropanenitrile
- KCN
- ethanolic
test for primary and secondary alchols
- add potassium dichromate
- gently warm
*H2SO4
- whats the mistake in this test and what is it supposed to test for
- add fehlings solution and cool in iced water
- not supposed to cool instead you need to warm
- it test for aldehydes and ketone
- brick red for aldehydes
what is one possible environmental problem with the complete combustion of biofuels made from sewage sludge
causes acid rain as SO2 is made
what would methanol dissolve
methanol is a polar solvents so it will only dissolve polar molecules and non polar solvents dissolve non polar solvents
what is a free radical
a molecule with an unpaired electron
why would you add anydrous calcium chloride at the end of a ethyl enthanoate esterification reaction
its a drying agent so it will remove any water
why might a reaction not have a 100% percentage yield
- its a reversible reaction
- side reactions
- product lost during separation
why are racemic mixtures formed
they have a planar shape so they can be attacked from either side with equal probability
how is the strength for a base determined
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)
deduce the type of interaction that occurs between a lysine R group and an aspartic acid R group
ionic bonding
name the other substance formed when 2 amino acids react together to form part of a protein chain
water
what is the type of reaction between an ester and a hydroxide
hydrolysis
a triester in vegetable oil reacts with sodium hydroxide give one use of the product of the reaction
soap
when doing titrations why would using a smaller target titre wouldn’t be appropriate
similar titre will increase uncertainty
what is a disadvantage of using a tripod and gauze when calculating enthalpy of combustion
tripod and gauze would reduce heat transfer
why is benzene more stable that kekules structure
because benzene has a ring of delocalised electrons
why do chemists design production methods with fewer steps
less energy used or better yeild
why do chemists design production methods with higher percentage atom economy
less waste or less pollution
