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AQA Chemistry Unit 3 GCSE 24.05.12

Any Thoughts on the Chemistry paper?

My Calculation Answers
Concentration: 0.61
Mass: 12g
Energy Change: -810KJ

Anyone have any other answers? :biggrin:

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Reply 1

maxtate

Original post by emily_p3

Any Thoughts on the Chemistry paper?

My Calculation Answers
Concentration: 0.61
Mass: 12g
Energy Change: -810KJ

Anyone have any other answers? :biggrin:

I got the same :smile:

(btw on the mark scheme it says ignore (-) or (+) 810, so I just left it as 810 LOL xD

Reply 2

SaraBB

i got 0.61, but how did you get 12g, lots of people i spoke to got 48g, knowing me i've done it wrong, but i did 0.61 times by the relative formula mass???
please explain :P

also, what do you think the ums points/grade boundaries will be for this paper?

Reply 3

elkana

in the last question how could the reaction have released heat if the energy before was less then the bond energy afterwards

Reply 4

emily_p3

Original post by SaraBB

well because 48gs would be 1000g so you had to divide it by 4 to get 12g :smile:

I think that they will be 35 for an A* and 40-42 for 100 ums

Reply 5

maxtate

Original post by SaraBB

Basically, cuz it didnt say 'use your answer from part (a i), u didnt have to use 0.61... sooo
the relative formula mass was 60, volume 250cm3, and concentration 0.8 mol/dm3,

You do 0.8 multiplied by 60, which is 48, and because 250*4 = 1000 (1000cm3 in a dm3), you do 48/4, which is 12 :smile:

(Dw that shoukdnt really have come up :/ but mehh it was in the CGP book new spec :smile:

Reply 6

maxtate

Original post by elkana

in the last question how could the reaction have released heat if the energy before was less then the bond energy afterwards

It wasnt, the energy required to break bonds was higher than energy released from making... :smile:

Reply 7

emily_p3

because it needed energy for the reaction to take place-activation energy

Reply 8

Fifi96

Original post by maxtate

I got the same :smile:

(btw on the mark scheme it says ignore (-) or (+) 810, so I just left it as 810 LOL xD

i put 810 are you sure they ignore the symbols? :/ hope so haha x

Reply 9

maxtate

Original post by emily_p3

because it needed energy for the reaction to take place-activation energy

I couldnt think of the word LOOL so I wrote, this heat energy is required to trigger the reaction :biggrin:

Reply 10

maxtate

Original post by Fifi96

i put 810 are you sure they ignore the symbols? :/ hope so haha x

Yehh definitely dont worry =P x

Reply 11

emily_p3

Original post by maxtate

I couldnt think of the word LOOL so I wrote, this heat energy is required to trigger the reaction :biggrin:

haha you should still get it because that is what activation energy is:P

Reply 12

elkana

Original post by maxtate

It wasnt, the energy required to break bonds was higher than energy released from making... :smile:

what? breaking bonds requires energy?
oh well :s-smilie:

thanks

Reply 13

maxtate

Original post by elkana

what? breaking bonds requires energy?
oh well :s-smilie:

thanks

Yhh dww most of the country probs got wrong LOOL basically, the misconception is that breaking bonds releases energy, but actually, making bonds releases energy, and breaking requires hahaa i only learnt that like last week :/

Reply 14

SaraBB

for the two tests it asked about, the first one i think she said it had aluminum ions...i put no because the precipitate didn't turn from white to colourless, it stayed white

and the second one (i think it was chloride ions) i put yes it did have them cause it formed a white precipitate (for the halide test)

please tell me i got something right...

(edited 11 years ago)

Reply 15

emily_p3

i just a bit confused, it said prove that the reaction is exothermic basically, so isn't that less energy was absorbed breaking existing bonds than energy released making new bonds

Reply 16

Wintabix

Hey, for the silver nitrate question, did you guys put yes? Because I thought if you add silver nitrate and forms a white precipitate, there're chloride ions present :P

Reply 17

emily_p3

i dont think that is was aluminum ions because it said that it didnt turn colourless in excess :s-smilie:

and when HCl and silver nitrate is added it forms a white silver chloride precipitate

Reply 18

flumpyfi

Can someone please tell me if I’d get the mark for these dodgy answers:

Why the student was surprised
Because the solubility increased as the temperature increased but decreased when the temperature reached 68 degrees – the solubility rose then fell.

2a) (Alkali metal properties)
-Very reactive
-Low melting points and boiling points

3a) (Properties of transition metals)
-Malleable so can be easily shaped into a ring.
-Very unreactive so will last longer.

4b) (pH of weak acids and strong acids)
-Weak acid will have a higher pH than a strong acid BECAUSE a strong acid completely ionises in water forming H+ ions whereas a weaker acid only partially dissociates forming H+ ions.