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AQA A-level Chemistry new 1 7405/1 - 13 & 19 Jun 2017 [Exam Discussion]

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Reply 1640

tsr120

Original post by Roman hang Limbu

Yep that makes sense, a long winded method but it would work in real life i guess lol.

haha if you come across a shorter method do share

Reply 1641

Jayo573

Does anyone know where an unofficial mark scheme is?

Reply 1642

Roman hang Limbu

Does anyone have a method on how to work out A and C? This is one the examples where they change concentration for every single one...Can anyone help me please..Thanks

Reply 1643

study_x

Original post by AR123456789

Hope it helps and hopefully it's correct anyway I don't think this'll come up since it was is paper 1.

thankss

Reply 1644

study_x

Original post by desigenius

Here is how you do it.. the other reply you got is wrong.

Office Lens 20170624-193452.jpg

Thank youu

Reply 1645

Swissblade

Original post by Roman hang Limbu

Does anyone have a method on how to work out A and C? This is one the examples where they change concentration for every single one...Can anyone help me please..Thanks

(Assuming that you've worked out that the order with respect to B = 1.)

For experiments 2 and 3, [C] remains constant. You know the order with respect to B = 1, and since is doubled,

3.20\times10^{-3} \times 2 = 6.4\times10^{-3}

. But, the initial rate is 4 times less, and since [A] is halved, you can deduce from this that the order with respect to A is 2, since

0.5^2 = 0.25 \rightarrow 0.25 \times 6.4\times10^{-3} = 1.6\times10^{-3}

.

I'll let you try the rest. Use experiments 3 and 4 to find C.

(edited 6 years ago)

Reply 1646

igotnomoney

Original post by Roman hang Limbu

Does anyone have a method on how to work out A and C? This is one the examples where they change concentration for every single one...Can anyone help me please..Thanks

Don't let it put you off, you could workout 9rder of other first and then determine others

Reply 1647

igotnomoney

Guys can you help me out, can somebody kindly post all the method for each practical so I could go through it ... it would be very helpful .. thankyou

Reply 1648

doglover123

How is everyone practicing calculation questions? They threw me off in the last 2 exams, especially that 8 marker, and most old spec questions seem too easy

Reply 1649

doglover123

Original post by igotnomoney

Guys can you help me out, can somebody kindly post all the method for each practical so I could go through it ... it would be very helpful .. thankyou

chemrevise has them all, but you'll have to look at the specific topic as its not in all in one booklet

Reply 1650

igotnomoney

I just read somewhere that if you change volume and initial concentration remains same the rate of reaction will be affected. Why is this , surely if you change volume pressure would be affected so therefore more molecules will have energy greater than activational energy hence higher succesful collisions.??

Reply 1651

tsr120

Original post by igotnomoney

I am not 100% sure but I think the issue may be regarding the rate equation. For example if rate = k x conc of A x conc of B, you can see the rate is only dependent on the conc of those two species; not the total volume. Does that make any sense?

Reply 1652

kiiten

Ready for paper 3 everyone? :tongue:

Its my last A level exam.

Reply 1653

igotnomoney

Original post by kiiten

Ready for paper 3 everyone? :tongue:

Its my last A level exam.

Yeah it's my last exam too. I don't know I'm feeling bit scared because I feel like I'm forgetting things lol .. I've done so well in paper 1 and paper 2 and I think this paper will screw me over and I will lose my A star or even A

Reply 1654

tthompson.2

What's everyone revising for inorganic chemistry?

Reply 1655

Mina_

Quick question: In the iodine clock reaction, we add different volumes of water in each mixture. Why is this? I know its to get each mixture to the same volume but why?

Reply 1656

haes

Original post by Mina_

Quick question: In the iodine clock reaction, we add different volumes of water in each mixture. Why is this? I know its to get each mixture to the same volume but why?

The independent variable is concentration. By using different volumes you get different concentrations

Reply 1657

icequeenTM

Guys do you think transition metals may make an appearance again??? I know there was a whole question on it but I don't know I feel like AQA loves them 😂😂

Reply 1658

Jcup

Does anyone by chance have the set 2 version of the paper 3 specimen and mark scheme and are able to send it to me? I'd really appreciate it :smile:

or just post it here or whatevs thankyou

Reply 1659

Enderbat1999

Original post by Stannis98

Guys do you think transition metals may make an appearance again??? I know there was a whole question on it but I don't know I feel like AQA loves them 😂😂

yes cus not much came on it i think itll be like using spectrophotometry and like why we see ceratin colours and not other and go over ahrenius jus incase and iodine stop.

i doubt ph or titrations will come up gain, cus they were in spec paper twice and ph came up in paper 1 too. Maybe go over calorimetry and like autocatalysis reactions, they are preety ez marks if u learn it and i have a feeling electrochemical cells are coming up again