AS Chemistry- helping each other out!
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Original post by Adamkahn
Anyone who's done the A2 bio or Chem will exchange info for AS bio and chem
Why exchange why not help someone out anyway lmfao.
I don't need it anyway did it a year early. But just saying.
Original post by ThatGuyRik
Why exchange why not help someone out anyway lmfao.
I don't need it anyway did it a year early. But just saying.
I don't need it anyway did it a year early. But just saying.
Your avi pic is more complicated than AS Chem.
I just did the task 3 aqa empa today, didn't seem that bad although i didn't do great
Ok.
I need help with equlibrium if any is willing.
Ok so a exothermic reaction has a positive enthalpy change and endothermic has negative
How do u know if increase/decrease in temp favours the forward/backwards reaction? ??
Thanks
I need help with equlibrium if any is willing.
Ok so a exothermic reaction has a positive enthalpy change and endothermic has negative
How do u know if increase/decrease in temp favours the forward/backwards reaction? ??
Thanks
Original post by Gladiatorsword
Ok.
I need help with equlibrium if any is willing.
Ok so a exothermic reaction has a positive enthalpy change and endothermic has negative
How do u know if increase/decrease in temp favours the forward/backwards reaction? ??
Thanks
I need help with equlibrium if any is willing.
Ok so a exothermic reaction has a positive enthalpy change and endothermic has negative
How do u know if increase/decrease in temp favours the forward/backwards reaction? ??
Thanks
Firstly an exothermic enthalpy change actually is defined as a negative enthalpy change. Le chateliers principal states that an equilibrium will react in such a way as to minimise any disturbance you create, so if you increase the temp it will try and reduce the temp by moving towards the endothermic direction as this absorbs heat and will reduce the temp. And vice versa for decreasing temp.
Posted from TSR Mobile
exothermic means that heat is being lost from the system. so it actually has a negative enthalpy change.
endothermic means that the heat of the system increases, so it has a positive enthalpy change.
when an system in equilibrium's temperature is increased, it wants to make that temperature go back down again. This means that the eq.position will move to the endothermic side because it will use up the heat and reduce the temperature.
Is that clear?
endothermic means that the heat of the system increases, so it has a positive enthalpy change.
when an system in equilibrium's temperature is increased, it wants to make that temperature go back down again. This means that the eq.position will move to the endothermic side because it will use up the heat and reduce the temperature.
Is that clear?
Original post by Gladiatorsword
Ok.
I need help with equlibrium if any is willing.
Ok so a exothermic reaction has a positive enthalpy change and endothermic has negative
How do u know if increase/decrease in temp favours the forward/backwards reaction? ??
Thanks
I need help with equlibrium if any is willing.
Ok so a exothermic reaction has a positive enthalpy change and endothermic has negative
How do u know if increase/decrease in temp favours the forward/backwards reaction? ??
Thanks
Okay so firstly you have the enthalpy changes the wrong way around, an exothermic reaction has a negative enthalpy because it is releasing energy and an endothermic reaction has a positive enthalpy because it is taking in energy to break bonds.
As for what conditions favor a reaction, I'm afraid you'll have to learn them off by heart the main ones you'll need to know are:
- If the forward reaction is exothermic and gives out heat (e.g. temp increase), when you increase the temp, the system will minimize the change and decrease it sending the equilibrium in the opposite direction which is the backward endothermic reaction, which is not very useful in the industry as you want as much product as possible no reactants. An example you may see in A level is the Haber process which is the industrial production of ammonia which is favored by low temps because the forward reaction is exothermic -ve
-Catalysts don't affect equilibrium
Original post by Frosty_A
So, what you are saying is:
First we must work out the moles of Sodium Hydroxide. We then used the mole ratio, to determine, the same amount of moles of HCL was used.
Then you worked out the moles of the HCl of the 250cm3, to give us the moles within that volume.
then you worked out the moles in 50cm3 hcl of 1.00m concentration.
But how does taking away 3.08x10-2 from 0.05, give us moles reacted?
First we must work out the moles of Sodium Hydroxide. We then used the mole ratio, to determine, the same amount of moles of HCL was used.
Then you worked out the moles of the HCl of the 250cm3, to give us the moles within that volume.
then you worked out the moles in 50cm3 hcl of 1.00m concentration.
But how does taking away 3.08x10-2 from 0.05, give us moles reacted?
Let's say for the sake of simplicity there were 10 moles of HCl to begin with.
You add the tablet and calcium hydroxide inside the tablet reacts with X moles of the HCl. Now 10-X moles of HCl is left in the container.
You will titrate the 10-X moles of HCl. 10-X moles of NaOH will be required. You have titrated the 10-X moles of HCl. 8 moles of NaOH was required for this.
X is the amount of HCl reacted with the calcium hydroxide. How do you get X?
10-X=8
so
X=10-8=2moles
.....
This is whats happening in the calculation in the first part. Number is a bit more complicated and short hand writing makes it confusing I guess.
Original post by Feraligatr
Yeah I guess 
Just make sure you do loads of past papers and understand where you're going, it helps
Just make sure you do loads of past papers and understand where you're going, it helps
Yep, gonna try to do every one from the AQA website (Already done 3 but gotta print the rest off in school
)Original post by Dinaa
u'd get emotionally fekd
chemically rekt
^lol not srs
chemically rekt
^lol not srs
Lol sure thing kid, u see i am a changed man u thought u knew me but u don't kid
Original post by ozzie2
Yep, gonna try to do every one from the AQA website (Already done 3 but gotta print the rest off in school )
Lol sure thing kid, u see i am a changed man u thought u knew me but u don't kid
)Lol sure thing kid, u see i am a changed man u thought u knew me but u don't kid
LOOOOOOOOOOOOL don't call me kid, kid.
I still have that edit of you
'wen u see da dih'
don't make me rek u bad KID.
Original post by thatgr
I just did the task 3 aqa empa today, didn't seem that bad although i didn't do great
Incoming 300 private messages from people asking for answers. But I'm sure you did fine and if you didn't do as well as you hoped, it is only worth 20% as far as I know and if you do well in the exams you should still be able to get a good grade
Original post by ozzie2
Yep, gonna try to do every one from the AQA website (Already done 3 but gotta print the rest off in school )
)Same here, I've done most questions from past papers but I wanna do one under exam conditions though
UGH I DIDN'T DO ANYTHING BUT PROCRASTINATE ON HERE AND SQUAT TODAY 
dead
dead
Original post by EmilyPBonner
Okay so firstly you have the enthalpy changes the wrong way around, an exothermic reaction has a negative enthalpy because it is releasing energy and an endothermic reaction has a positive enthalpy because it is taking in energy to break bonds.
As for what conditions favor a reaction, I'm afraid you'll have to learn them off by heart the main ones you'll need to know are:
- If the forward reaction is exothermic and gives out heat (e.g. temp increase), when you increase the temp, the system will minimize the change and decrease it sending the equilibrium in the opposite direction which is the backward endothermic reaction, which is not very useful in the industry as you want as much product as possible no reactants. An example you may see in A level is the Haber process which is the industrial production of ammonia which is favored by low temps because the forward reaction is exothermic -ve
-Catalysts don't affect equilibrium
As for what conditions favor a reaction, I'm afraid you'll have to learn them off by heart the main ones you'll need to know are:
- If the forward reaction is exothermic and gives out heat (e.g. temp increase), when you increase the temp, the system will minimize the change and decrease it sending the equilibrium in the opposite direction which is the backward endothermic reaction, which is not very useful in the industry as you want as much product as possible no reactants. An example you may see in A level is the Haber process which is the industrial production of ammonia which is favored by low temps because the forward reaction is exothermic -ve
-Catalysts don't affect equilibrium
Ok. Say you're given a reaction with an negative enthalpy change - its exothermic. But how do you know if the forward reaction is exothermic or the backwards? ??
Posted from TSR Mobile
Original post by Gladiatorsword
Ok. Say you're given a reaction with an negative enthalpy change - its exothermic. But how do you know if the forward reaction is exothermic or the backwards? ??
Posted from TSR Mobile
Posted from TSR Mobile
General convention is that you're given the change for the reaction going from left to right
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Original post by Dinaa
LOOOOOOOOOOOOL don't call me kid, kid.
I still have that edit of you
'wen u see da dih'
don't make me rek u bad KID.
I still have that edit of you
'wen u see da dih'
don't make me rek u bad KID.
Uhm what are you talking about, wot pic. Also what happened to those kik group chats? I miss them and u bullying me
Original post by Gladiatorsword
Ok. Say you're given a reaction with an negative enthalpy change - its exothermic. But how do you know if the forward reaction is exothermic or the backwards? ??
Posted from TSR Mobile
Posted from TSR Mobile
It should always mention it in the question, if there is an enthalpy change next to the reaction you can assume that is for the forward reaction.
Original post by ozzie2
Uhm what are you talking about, wot pic. Also what happened to those kik group chats? I miss them and u bullying me
Hah they died.
Wut you don't remember the famous dina photoshop of you?
I COULD ALWAYS POST AND SHOW YOU?
Original post by EmilyPBonner
It should always mention it in the question, if there is an enthalpy change next to the reaction you can assume that is for the forward reaction.
Is it awkward having a surname as Boner?
Original post by Gladiatorsword
Ok. Say you're given a reaction with an negative enthalpy change - its exothermic. But how do you know if the forward reaction is exothermic or the backwards? ??
Posted from TSR Mobile
Posted from TSR Mobile
As said above it will always be said or shown. For example, it may show deltah=-45. Because it's - sign, we know it's an exothermic reaction.
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