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AQA AS Chemistry: 8th June

Reply 60

daaavo

soz... im tired... thought u sed fermentation........

Reply 61

Kiesha

10

franks

lol exactly my next question!
Ionisation-high energy electrons fired from electron gun
-knocks out an electron forming positive ions

Acceleration-by electric field
-accelerated towards negatively charged plates
-focused into a beam

Deflection-by magnetic field
-depends on m/z ratio
-smaller m/z value the greater the deflection

Detection-ions hit a plate and induces a current
-graph plotted m/z against abundancies

erumm next question... how does fractional distillation work

Hehe!

Erm ... fractional distillation: Crude oil heated and vapourised in fractionating column - hottest at the bottom, cooler at the top. Smaller fractions with lower b.pts move further up the tower and the longer chained hydrocarbons with high b.pts are towards the bottom. The fractions are tapped off. Cracking of longer hydrocarbons to produce shorter, more useful ones to keep up with demand.

Define activation energy. Give 3 factors which affect the rate of reaction and explain why they do.

Reply 62

daaavo

min energy required for a reaction to take place when two particles collide; temp affects rate... more vigorous collisions, as does catalyst.... route with lower Eact and concentration.... more frequent collisions resulting in reaction

Reply 63

kiaora

1

daaavo

glocose (in aq. solution) converted by anaerobic respiration of yeast into Carbon dioxide and c2h5oh. Enzyme in yeast which does this.... temp no more than 40degrees c because yeast denatures... conc of ethanol can't get too high either or yeast dies

direct hydration of ethene

C2H4 + H2O --> 2 C2H5OH + 2 CO2

300.C
6500kPa

Reply 64

Twiglet

2

temp affects rate... more vigorous collisions,

increased temperature increases the number of particles with the activation energy so more collisions are successful

as does catalyst

catalyst increases rate by providing an alternative route with lower activation energy so more particles have the activation energy so more collisions are successful

Reply 65

Twiglet

2

Why does NH3 react in the way it does when added to a haloalkane?

Reply 66

daaavo

why does AlCl3 have covalent character?

Reply 67

Kiesha

10

The C-X bond in a haloalkane is polarised so the NH3 acts as a nucleophile (because it has a lone pair) and attacks the positively polarised C.

Reply 68

kiaora

1

franks

Why does NH3 react in the way it does when added to a haloalkane?

it has a lone pair of electrons on the N. it has to be heated at 100.c in a sealed container as there is no charge on the NH3.

Reply 69

Twiglet

2

why does AlCl3 have covalent character?

Well its not ionic because Al and Cl dont have a large enough difference in electronegativities.
Its to do with 'anions are distorted by cations of high charge density', since the Al has a high charge density it attracts the cloud of electrons around the chlorine so much that they share the electron and a covalent bond is formed.
Hmm I think im gonna go do some proper work now... good luck everybody :biggrin:

franks x

Reply 70

Kiesha

10

franks

Well its not ionic because Al and Cl dont have a large enough difference in electronegativities.
Its to do with 'anions are distorted by cations of high charge density', since the Al has a high charge density it attracts the cloud of electrons around the chlorine so much that they share the electron and a covalent bond is formed.
Hmm I think im gonna go do some proper work now... good luck everybody :biggrin:

franks x