Hey there! Sign in to join this conversationNew here? Join for free
    Offline

    1
    ReputationRep:
    (Original post by ryanb97)
    You only need an A to get your A* ... this time round
    Oh really?? I hope I do. I've only done c4 though. Need to start ASAP
    Offline

    2
    ReputationRep:
    Ok my teacher and revision guide are telling me opposite things, is anybody able to explain this:
    'Explain the changes that take place at each electrode in a hydrogen-oxygen fuel cell: 1.) Construct the equations for the electrode reactions, given the formulae of the ions present and the products, and 2.) Redox reactions at each electrode.'
    Offline

    16
    ReputationRep:
    (Original post by L'Evil Fish)
    Well, it won't bond ionically
    urgh i find chemistry hard -_- it just depends on the exam i guess!
    Offline

    0
    ReputationRep:
    (Original post by L'Evil Fish)
    Okay:

    Positive = Anode
    Negative = Electrode

    Electrolysis is breaking down through electricity.

    I'll start with the easiest to understand.

    Molten Lead Bromide = PbBr(2)

    It's an ionic bond made up of ions:
    Pb2+ and Br-

    So these are now molten and flowing freely.

    The Pb2+ is positive and so is attracted to the cathode. It gains 2 electrons there and becomes lead (no charge). Lead is reduced.

    The Br- ions are negative and are attracted to the anode. It gives an electron to the anode and becomes Br (no charge). It is oxidized.

    Yeah?
    Thanks this makes it so much easier.
    • Thread Starter
    Offline

    18
    ReputationRep:
    (Original post by AsianNoodles)
    Thanks this makes it so much easier.
    It's the same with other solutions, but there are also OH- and H+ ions as well then from water.
    Offline

    1
    ReputationRep:
    Just got back from Geography. Time to do chemistry revision!


    Posted from TSR Mobile
    Offline

    0
    ReputationRep:
    Can anyone help me with Equilibrium?

    I know for the Haver Process that pressure moves it right and temperature left and, like always, the catalyst doesn't move it, but what do the different conditions do for theContact Process?

    thanks in advance
    Offline

    2
    ReputationRep:
    (Original post by dazzer19)
    Can anyone help me with Equilibrium?

    I know for the Haver Process that pressure moves it right and temperature left and, like always, the catalyst doesn't move it, but what do the different conditions do for theContact Process?

    thanks in advance
    High temperatures move equilibrium to the left, but increase the rate of reaction. So a compromise is used.
    The catalyst doesn't move the position but increases rate of reaction.
    Even at low pressure, the Contact Process has the position of equilibrium on the right side, so expensive high pressure isn't used. Atmospheric pressure is used
    Offline

    13
    ReputationRep:
    (Original post by Knowing)
    Just got back from Geography. Time to do chemistry revision!


    Posted from TSR Mobile
    How did i go?
    Offline

    0
    ReputationRep:
    (Original post by BrokenS0ulz)
    High temperatures move equilibrium to the left, but increase the rate of reaction. So a compromise is used.
    The catalyst doesn't move the position but increases rate of reaction.
    Even at low pressure, the Contact Process has the position of equilibrium on the right side, so expensive high pressure isn't used. Atmospheric pressure is used
    Thanks haha, I still get a bit confused over the whole equilibrium topic tbh...

    If the equilibrium is on the left, does that mean that there are MORE reactants in relation to products? Or just more reactants in general?
    Offline

    13
    ReputationRep:
    (Original post by dazzer19)
    Thanks haha, I still get a bit confused over the whole equilibrium topic tbh...

    If the equilibrium is on the left, does that mean that there are MORE reactants in relation to products? Or just more reactants in general?
    It means that the rate of reaction from products into reactants is higher than the rate of reaction from reactants to products.
    Offline

    0
    ReputationRep:
    (Original post by andersson)
    It means that the rate of reaction from products into reactants is higher than the rate of reaction from reactants to products.

    Ah I see,

    one last thing,

    is it a recurring factors that:
    temperature always moves the equilibrium lleft and pressure always moves it right? Or does it change?

    like, we only neeed to know about the contact ad Haber processes, so in each one of these does the temp always move it left and pressure right? Thanks
    Offline

    13
    ReputationRep:
    (Original post by dazzer19)
    Ah I see,

    one last thing,

    is it a recurring factors that:
    temperature always moves the equilibrium lleft and pressure always moves it right? Or does it change?

    like, we only neeed to know about the contact ad Haber processes, so in each one of these does the temp always move it left and pressure right? Thanks
    Nope it's possible they could give you a random reversible reaction and ask you predict what effect increasing temperature, pressure etc will have on it, so you need to know what actually happens:

    Increasing the temperature makes the equilibrium move in the direction that is an endothermic and vice versa. This won't always be the backward reaction.

    Changing the pressure only has an effect on gases. Increasing it makes the equilibrium move in the direction with fewer moles i.e. whichever side has the smallest amount of molecules made.

    Hope that helps.
    Offline

    0
    ReputationRep:
    So In the electrolysis of sodium hydroxide, hydrogen is made rather than sodium. Why is that? :cool:
    Offline

    0
    ReputationRep:
    (Original post by andersson)
    Nope it's possible they could give you a random reversible reaction and ask you predict what effect increasing temperature, pressure etc will have on it, so you need to know what actually happens:

    Increasing the temperature makes the equilibrium move in the direction that is an endothermic and vice versa. This won't always be the backward reaction.

    Changing the pressure only has an effect on gases. Increasing it makes the equilibrium move in the direction with fewer moles i.e. whichever side has the smallest amount of molecules made.

    Hope that helps.
    Ahh ok, thank you!
    Offline

    1
    ReputationRep:
    (Original post by andersson)
    How did i go?
    It was OK. Not too bad.

    Unfortunately I don't think I did so well in Paper 1 so I don't know whether I'll get A* or not. We'll have to see


    Posted from TSR Mobile
    Offline

    16
    ReputationRep:
    (Original post by Turtlefushsia)
    So In the electrolysis of sodium hydroxide, hydrogen is made rather than sodium. Why is that? :cool:
    it is easier for the hydrogen ions to be given off rather than sodium.
    Offline

    16
    ReputationRep:
    (Original post by andersson)
    Nope it's possible they could give you a random reversible reaction and ask you predict what effect increasing temperature, pressure etc will have on it, so you need to know what actually happens:

    Increasing the temperature makes the equilibrium move in the direction that is an endothermic and vice versa. This won't always be the backward reaction.

    Changing the pressure only has an effect on gases. Increasing it makes the equilibrium move in the direction with fewer moles i.e. whichever side has the smallest amount of molecules made.

    Hope that helps.
    is there any way of figuring out which is exo and which is endo?
    Offline

    0
    ReputationRep:
    (Original post by benwalters1996)
    it is easier for the hydrogen ions to be given off rather than sodium.
    But why is that? Do we need to know
    Offline

    11
    ReputationRep:
    Got 69/85 on the specimen paper with a consistent 21 marks on each module. Feeling very confident of an A* now.
 
 
 
Poll
Do you agree with the PM's proposal to cut tuition fees for some courses?

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.