Turn on thread page Beta
    Offline

    2
    ReputationRep:
    because usually %uncertainty=error?reading

    the eroor is 5mg for would it just be 0.005g/ the reading x 100

    but it shows eroor to be 0.001
    Offline

    21
    ReputationRep:
    (Original post by dpoojaraa)
    I would disagree since we aren't looking at the end point but in fact the equivalence point. The equivalence point for the titration between a weak acid and strong base is 9 so from looking at the data booklet I would say the answer is C, thymol blue (base) since the pH range for thymol blue (base) is 8.0-9.6 and 9 is in that range (none of the other options have a suitable range). Hope that helps, @dinaa
    Yep, I agree with you, i was looking at end point. Woopsies.


    Posted from TSR Mobile
    Offline

    17
    ReputationRep:
    (Original post by Bloom77)
    Is the answer d) alizRin yellow R
    Because you are adding NaOH into ethanoic acid and NaOH is a strong base so the pH would go very high and by looking at the data booklet, the highest pH indication is D) alizarin yellow R


    Posted from TSR Mobile
    Oops I meant q18 and naw, the answer to 8 is C:3
    Offline

    13
    ReputationRep:
    (Original post by Dinaa)
    Oops I meant q18 and naw, the answer to 8 is C:3
    What have you tried so far? Is it the whole of 18 or just some parts
    Offline

    17
    ReputationRep:
    (Original post by samb1234)
    What have you tried so far? Is it the whole of 18 or just some parts
    I found the order wrt to [H+]

    It is [Br-] that is confusing me.

    Using experiment 1 and 3, the [H+] stays constant, [BrO3-] triples and [Br-] doubles. The rate is x6.
    I don't know how to link all this information together to get an order wrt [Br-].
    Offline

    4
    ReputationRep:
    (Original post by Thisshouldbeapun)
    Does anyone know what Kc actually is?
    I'm so confused because i thought it showed where the position of equilibrium was for a reaction but if that is the case then surely it would change with pressure/concentration because these move the position of equilibrium?
    Thanks


    Kc actually stands for concentration constant ........questions related to Kc and Kp are usually calculations i mean i think i never solved a paper where they ask for the definition or something and in multiple choice questions its usually like they ask which factor effect the Kc or Kp and the answer always stays the same that is temperature ....anyways generally Kc and Kp are called equilibrium constant ...value of Kc is calculated using the equilibrium concentrations of the products and reactant.
    Offline

    13
    ReputationRep:
    (Original post by Dinaa)
    I found the order wrt to [H+]

    It is [Br-] that is confusing me.

    Using experiment 1 and 3, the [H+] stays constant, [BrO3-] triples and [Br-] doubles. The rate is x6.
    I don't know how to link all this information together to get an order wrt [Br-].
    Well we are told in the question that the reaction is first order wrt [BrO3-], so if we just tripled BrO3 what would we expect the rate to be? Therefore what factor is the bromine responsible for
    Offline

    4
    ReputationRep:
    [QUOTE=Nightinwind;64956675]
    (Original post by alyoan tariq)

    so as it reduces chromium from +6 to +3 (orange to green) then the substance must be oxidised so it cannot be a ketone ( not c ) it reacts with HCN and KCN so must be a carbonyl but not ketone so has to be an aldehyde and as one mole of it reacts with two moles of HCN then there must be 2 aldehyde groups so answer is D ?
    thank u so much i got it .....yes the answer is D ......yea I already knew that it would be an aldehyde but I was confused on how it reacted in terms of the structural formula ....thank u once again ...
    Offline

    4
    ReputationRep:
    (Original post by Enderbat1999)
    can someone help me with percentage uncertainty
    for uncertainties all u have to know is this :
    in the case of addition or subtraction u add the absolute uncertainty ......
    in the case of division or multiplication u add up the % uncertainty
    u calculate the % uncertainity like this (absolute uncertainty/value*100)
    now for eg u have to calculate the percentage uncertainty of a line:
    2.59 +/- 0.1
    so the % uncertainity will be
    0.1/2.59*100 = 3.86%
    and the absoute uncertainity will be 0.1 in this case .....
    hope that helps ///
    Offline

    10
    ReputationRep:
    On edexcel past papers the number of decimal places they want your answer to be in seems to be constantly changing and is often not stated in the question.. This means I spend a lot of time wondering if I got the marks or not... could anybody explain what the phrase "IGNORE sf except 1 sf" means?

    EG, I round my answer to 0.015 and the mark scheme says 0.0149 but to "IGNORE sf except 1 sf"
    Offline

    3
    ReputationRep:
    For the AS AQA new spec, where can I find questions related to the practicals we did?
    Offline

    2
    ReputationRep:
    (Original post by alyoan tariq)
    for uncertainties all u have to know is this :
    in the case of addition or subtraction u add the absolute uncertainty ......
    in the case of division or multiplication u add up the % uncertainty
    u calculate the % uncertainity like this (absolute uncertainty/value*100)
    now for eg u have to calculate the percentage uncertainty of a line:
    2.59 +/- 0.1
    so the % uncertainity will be
    0.1/2.59*100 = 3.86%
    and the absoute uncertainity will be 0.1 in this case .....
    hope that helps ///
    Dood thanks that makes sense now thank you
    Offline

    21
    ReputationRep:
    Name:  ImageUploadedByStudent Room1463812031.432943.jpg
Views: 132
Size:  134.5 KB

    Would I still get the mark if I drew the arrow like this?


    Posted from TSR Mobile
    Offline

    2
    ReputationRep:
    No has to be on the diagram and one thing why is the arrow that way can you explain
    Offline

    16
    ReputationRep:
    (Original post by NimbleNeil)
    On edexcel past papers the number of decimal places they want your answer to be in seems to be constantly changing and is often not stated in the question.. This means I spend a lot of time wondering if I got the marks or not... could anybody explain what the phrase "IGNORE sf except 1 sf" means?

    EG, I round my answer to 0.015 and the mark scheme says 0.0149 but to "IGNORE sf except 1 sf"
    Usually, you round your answer according to data significant figures that is given in the question, if the question asked like there is 0.01 mol of Mg and 1.2 mol of Na, the both number of moles is to 2 s.f then you'll have to round your answer to 2 s.f , when the data in the question was given to different s.f, you have to round your answer to at least 3 s.f , and that's why in this case the mark scheme would say, accept any answer except to 1s.f which means if you have rounded your answer up to 1 s.f then it is rejected
    Offline

    21
    ReputationRep:
    (Original post by Enderbat1999)
    No has to be on the diagram and one thing why is the arrow that way can you explain
    Because the lone pair of electrons electrons is being donated to the N- from the nitrogen.


    Posted from TSR Mobile
    Offline

    2
    ReputationRep:
    For aqa
    How do you know when to use phenyl- and when to use -benzene

    In the textbook there's benzenecarboxylic acid, benzenecarbaldehyde, and a few other benzene ones then it has phenylamine
    Offline

    19
    ReputationRep:
    (Original post by Bloom77)
    Name:  ImageUploadedByStudent Room1463812031.432943.jpg
Views: 132
Size:  134.5 KB

    Would I still get the mark if I drew the arrow like this?


    Posted from TSR Mobile
    I doubt it. Why would you draw it like that?

    (Original post by olivia7001)
    For aqa
    How do you know when to use phenyl- and when to use -benzene

    In the textbook there's benzenecarboxylic acid, benzenecarbaldehyde, and a few other benzene ones then it has phenylamine
    If they ask you to name something, use phenyl.
    Offline

    2
    ReputationRep:
    guys can someone put all the equation we need to know with halogens. especially the redox ones with h2so4
    Offline

    0
    ReputationRep:
    why is the ionic equation of a metal carbonate+acid CO3^2- + 2H+ = H2O + CO2 if metal carbonates are solid and in ionic equations you only separate aqueous solutions?
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: April 22, 2018
The home of Results and Clearing

1,084

people online now

1,567,000

students helped last year

University open days

  1. University of Buckingham
    Postgraduate Open Evening Postgraduate
    Thu, 23 Aug '18
  2. University of Glasgow
    All Subjects Undergraduate
    Tue, 28 Aug '18
  3. University of Aberdeen
    Undergraduate Open Day Undergraduate
    Tue, 28 Aug '18
Poll
How are you feeling about GCSE results day?

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.