The Student Room Group

ocr a f325 revision thread

Scroll to see replies

Reply 300
Original post by otrivine
Anyone up for revision


EDIT: Case Closed - Found a link: http://www.thestudentroom.co.uk/showthread.php?t=1505772


Can you help me gf or ANYONE ! Edit I didn't know that if it was I2 then you had to do Mass / RFMx2 - Me being an Amateur, better now than in the exam, I'll leave it up for any one who needs practice its Mod 1

Page 161 of the text book Question 4e

7. Hydroiodic acid, HI(aq), is a strong acid that is an aqueous solution of hydrogen iodide. In the laboratory, hydroiodic acid can be prepared by the method below.

A mixture of 480 g of iodine and 600cm^3 of water was put into a flask. The mixture was stirred and hydrogen sulphide gas, H2S(g) was bubbled through for several hours.
The mixture became yellow as sulphur seperated out. The sulphur was filtered off and the solution was purified by fractional distillation. A fraction of HI(aq) was collected containing 440g of HI in a total volume of 750cm^3


(ii)Determine the percentage yield of hydroiodic acid.

(edited 10 years ago)
Reply 301
Guys for the equilibream constant Kc...if there is a solid involved in the equation you omit it from the Kc expression right? But what if the is a liquid involved by itself (ie not a solvent just the liquid eg. H20(l)...do you omit that as well from the Kc expression? Its easy for homogenous equilibrea but Im speaking in terms of Heterogenous equilibrea :smile: Thank you
Reply 302
Original post by Gulzar
Guys for the equilibream constant Kc...if there is a solid involved in the equation you omit it from the Kc expression right? But what if the is a liquid involved by itself (ie not a solvent just the liquid eg. H20(l)...do you omit that as well from the Kc expression? Its easy for homogenous equilibrea but Im speaking in terms of Heterogenous equilibrea :smile: Thank you


Heterogenous Equilibria are not in our Specification. I guess you are doing Old Syllabus questions?

Conc = Mol / Vol so you just put that into the equation of Kc that you state, normally in the first part of the question.

For each conc you are considering. If it has something to do with mass then you need to work out relevant mols (I would assume).
Original post by Better
EDIT: Case Closed - Found a link: http://www.thestudentroom.co.uk/showthread.php?t=1505772


Can you help me gf or ANYONE ! Edit I didn't know that if it was I2 then you had to do Mass / RFMx2 - Me being an Amateur, better now than in the exam, I'll leave it up for any one who needs practice its Mod 1

Page 161 of the text book Question 4e

7. Hydroiodic acid, HI(aq), is a strong acid that is an aqueous solution of hydrogen iodide. In the laboratory, hydroiodic acid can be prepared by the method below.

A mixture of 480 g of iodine and 600cm^3 of water was put into a flask. The mixture was stirred and hydrogen sulphide gas, H2S(g) was bubbled through for several hours.
The mixture became yellow as sulphur seperated out. The sulphur was filtered off and the solution was purified by fractional distillation. A fraction of HI(aq) was collected containing 440g of HI in a total volume of 750cm^3


(ii)Determine the percentage yield of hydroiodic acid.




To get the percentage yield , you need to calculate the number of moles and divide the small with big and that gives your yield
Reply 304
Original post by Better
Heterogenous Equilibria are not in our Specification. I guess you are doing Old Syllabus questions?

Conc = Mol / Vol so you just put that into the equation of Kc that you state, normally in the first part of the question.

For each conc you are considering. If it has something to do with mass then you need to work out relevant mols (I would assume).


Oh yeah and if the equilibream Kc has no units then the Vol cancels out in the Kc equation so effectively you dont need the Volume...that caught me out XD
Original post by Gulzar
Oh yeah and if the equilibream Kc has no units then the Vol cancels out in the Kc equation so effectively you dont need the Volume...that caught me out XD


Hi Gulzar, want to revise :smile:
hey
anyone got any revision packs/questions?

I'll love you forever and give u reps :smile:
Original post by AishaTara
hey
anyone got any revision packs/questions?

I'll love you forever and give u reps :smile:


Yes, lets revise :smile:

Define:Neutralisation (1)

What does Ka value show(1)
Reply 308
Original post by AishaTara
hey
anyone got any revision packs/questions?

I'll love you forever and give u reps :smile:


I prefer Rep.

Revision Pack here:
http://www.thestudentroom.co.uk/showthread.php?t=1964069

We're all gonna make it brah's and sisters
Original post by Better
I prefer Rep.

Revision Pack here:
http://www.thestudentroom.co.uk/showthread.php?t=1964069

We're all gonna make it brah's and sisters


people say when the paper is hard, it rapes candidates. This year we're gonna rape the papers and show dem examiners we are just as capable :wink:
Reply 310
Original post by AishaTara
people say when the paper is hard, it rapes candidates. This year we're gonna rape the papers and show dem examiners we are just as capable :wink:


Haha! I really hope so!!! :smile:

From the questions I've been doing so far, I think my Unit 4 retake my be harder than Unit 5! Need to start -re-learning Unit 4 ASAP

But lets do this! :angry: x
Original post by Better
Haha! I really hope so!!! :smile:

From the questions I've been doing so far, I think my Unit 4 retake my be harder than Unit 5! Need to start -re-learning Unit 4 ASAP

But lets do this! :angry: x


want to revise! Better?
Reply 312
Original post by otrivine
want to revise! Better?


Not good enough yet. Just had a 3 hour nap and was supposed to do Mod 2.

:frown: :frown: :frown:
Reply 313
can anyone send the jan 2013 paper and mark scheme to me on here please?
Original post by emah123
can anyone send the jan 2013 paper and mark scheme to me on here please?


want to revise
Reply 315
Original post by emah123
can anyone send the jan 2013 paper and mark scheme to me on here please?



If you get the paper and mark scheme, could you let me know please and pass it on if you don't mind?
Reply 316
Original post by otrivine
Describe how you would carry out an experiment in order to determine if the reaction is first order for rate aganist concentration (4)

Sorry for the late reply guys, I'm a real menace with technology sometimes! Also, I bought some really engrossing books in London... back to topic!

1. Add the same concentration of (reactant A) to a conical flask and then add a volume of (reactant B) which will react to give a precipitate.
2. Measure the amount of time between adding B to A and a precipitate being formed, and record this as the rate of reaction.
3. Repeat at different concentrations of B and record results, whilst keeping [A] constant.
4. If the reaction is first order with respect to B, doubling will effect a twofold increase in the reaction rate.

How's that?

Q: Explain why transition metals often yield coloured compounds.
Original post by MathsNerd1
Can I ask you one too? Or would it be too many people asking questions at the same time? If its fine then:

Explain the effects of ionic size and ionic charge on the size of lattice enthalpy. (4)


Posted from TSR Mobile

Sorry for the late reply sir, I hope I've not ruined your revision session with Otrivine! :frown:

Well... if the ionic charge is larger, then the ions will experience a greater attraction to each other and the lattice enthalpy will be larger as more energy will be released when they become a solid compound. If the ionic radius is larger, the lattice enthalpy will be smaller as the attractive force of the ionic charges will have to act over a larger radius? I haven't looked at this in a while if I'm honest, you can probably tell!

Q: Describe the graphs for rate vs. time for first, second and zero order reactions.
Original post by IQ Test
Sorry for the late reply guys, I'm a real menace with technology sometimes! Also, I bought some really engrossing books in London... back to topic!

1. Add the same concentration of (reactant A) to a conical flask and then add a volume of (reactant B) which will react to give a precipitate.
2. Measure the amount of time between adding B to A and a precipitate being formed, and record this as the rate of reaction.
3. Repeat at different concentrations of B and record results, whilst keeping [A] constant.
4. If the reaction is first order with respect to B, doubling will effect a twofold increase in the reaction rate.

How's that?

Q: Explain why transition metals often yield coloured compounds.

Sorry for the late reply sir, I hope I've not ruined your revision session with Otrivine! :frown:

Well... if the ionic charge is larger, then the ions will experience a greater attraction to each other and the lattice enthalpy will be larger as more energy will be released when they become a solid compound. If the ionic radius is larger, the lattice enthalpy will be smaller as the attractive force of the ionic charges will have to act over a larger radius? I haven't looked at this in a while if I'm honest, you can probably tell!

Q: Describe the graphs for rate vs. time for first, second and zero order reactions.


correct!

its fine :smile:

Its because they have a partially filled d sub shell and also they absorb light at different wavelengths, when there is a mixture of colour in the test tube this means that , there is no absorbtion and so is reflected in the electromagnetic spetrum for example copper (II) sulfate is a green substrnace and when reflected gives a blue coloured solution
Reply 318
Original post by otrivine
correct!

its fine :smile:

Its because they have a partially filled d sub shell and also they absorb light at different wavelengths, when there is a mixture of colour in the test tube this means that , there is no absorbtion and so is reflected in the electromagnetic spetrum for example copper (II) sulfate is a green substrnace and when reflected gives a blue coloured solution

Exactly!

By the way, what do you want to do in the future? :smile:
Original post by IQ Test
Exactly!

By the way, what do you want to do in the future? :smile:


Pharmacist and doctor :cool:
(edited 10 years ago)

Quick Reply