AS Chemistry- helping each other out!
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Original post by Super199
For titrations what is the table you have to do. I have the empa coming up 
Generally, you'd have the first column as being titre (this starts with 'rough' then 1, 2, 3 etc). The next column should be start volume, then finish volume, then you work out the volume used. If you are doing this multiple times, you could also have an average titre column.
does anyone have chemistry unit 3B notes, as in detailed ones about core practicals??
what are you predicted so far??
hi i got a question to ask,
does anyone know the percentage yield difference formula??
does anyone know the percentage yield difference formula??
Original post by HToo
hi i got a question to ask,
does anyone know the percentage yield difference formula??
does anyone know the percentage yield difference formula??
Like how to calculate % yield?
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% yield = actual yield (obtained from carrying out experiment) / theoretical yield (calculated from the numbers provided in the question)
If you have a specific question that you're stuck on, I could work it out for you and show you the stages if you want.
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If you have a specific question that you're stuck on, I could work it out for you and show you the stages if you want.
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Original post by Fiellabella
If you have a specific question that you're stuck on, I could work it out for you and show you the stages if you want.
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Example I made the other day to help someone
I can help you. Example question:
The equation for the reaction of CuCO3 and H2SO4 is shown below:
CuCo3 +H2SO4 goes to H2O + CO2 + CuSO4.
Given that John reacts 2.2g of CuCO3, calculate the theoretical yield of CuSO4.
Solution: the first thing to do is look at the mole ratios of each of the reactants and products. In this case, there is 1 mole of everything (large number in front of the formula is the no of moles) so it follows that the number of moles of CuCO3 must = no of CuSO4. Next, calculate how many moles of CuCO3 you have by dividing 2.2 by the total Mr of CuCO3 (don't have a calculator so I'll leave it like that). You now know the no of moles of CuCO3 and hence the number of moles of CuSO4. To work out the theoretical yield, multiply the number of molesby the total Mr of CuSO4.
Question 2: After experiment, John weighed his CuSO4 crystals and found that he had 0.6g of crystals. Calculate the % yield.
Solution: % yield = theoretical yield/actual yield *100
Hope that helps
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Anyone done ocr f322 JANUARY 2011 question 3ciii? Why does the result for enthalpy change of reaction have to be multiplied by 2? Shouldn't it just be per mole?
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Original post by anoymous1111
Anyone done ocr f322 JANUARY 2011 question 3ciii? Why does the result for enthalpy change of reaction have to be multiplied by 2? Shouldn't it just be per mole?
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You might get a quicker response if you uploaded a screenshot or something
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I don't understand part ciii.... normally I find these calculations easy and I worked out what I thought was the enthalpy change per mole. However on the mark scheme this answer is multiplied by 2. I can see in the equation there is a 2NH4SCN, but I thought it would still just be the enthalpy change per mole. Surely multiplying it by 2 means it isn't the enthalpy change per mole? Do you always have to do this with enthalpy of reaction questions?
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Often this is because of a 2:1 molar ratio
Original post by anoymous1111
I don't understand part ciii.... normally I find these calculations easy and I worked out what I thought was the enthalpy change per mole. However on the mark scheme this answer is multiplied by 2. I can see in the equation there is a 2NH4SCN, but I thought it would still just be the enthalpy change per mole. Surely multiplying it by 2 means it isn't the enthalpy change per mole? Do you always have to do this with enthalpy of reaction questions?
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I don't understand part ciii.... normally I find these calculations easy and I worked out what I thought was the enthalpy change per mole. However on the mark scheme this answer is multiplied by 2. I can see in the equation there is a 2NH4SCN, but I thought it would still just be the enthalpy change per mole. Surely multiplying it by 2 means it isn't the enthalpy change per mole? Do you always have to do this with enthalpy of reaction questions?
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http://gyazo.com/e29c3ce9c8848d8c7e45ec70dacdad2e per mole accepted
Original post by ftsoft
http://gyazo.com/e29c3ce9c8848d8c7e45ec70dacdad2e per mole accepted
The definition of enthalpy of reaction is the enthalpy change when equation quantities of reactants react. Therefore since in the equation there are 2 you must double it.
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Hi everyone,
Was suggested here. I have so many questions to ask it's unbelievable. But first I wanted to know are there any chemical formulas or equations we need to learn or is it something we could work out using the periodic table? I know I shouldn't be asking these basic questions but I'm so basic right now it's sad. I'm looking through the textbook at the moment- on page one. OCR A.
Was suggested here. I have so many questions to ask it's unbelievable. But first I wanted to know are there any chemical formulas or equations we need to learn or is it something we could work out using the periodic table? I know I shouldn't be asking these basic questions but I'm so basic right now it's sad. I'm looking through the textbook at the moment- on page one. OCR A.
Original post by Cherry82
Hi everyone,
Was suggested here. I have so many questions to ask it's unbelievable. But first I wanted to know are there any chemical formulas or equations we need to learn or is it something we could work out using the periodic table? I know I shouldn't be asking these basic questions but I'm so basic right now it's sad. I'm looking through the textbook at the moment- on page one. OCR A.
Was suggested here. I have so many questions to ask it's unbelievable. But first I wanted to know are there any chemical formulas or equations we need to learn or is it something we could work out using the periodic table? I know I shouldn't be asking these basic questions but I'm so basic right now it's sad. I'm looking through the textbook at the moment- on page one. OCR A.
Well first calm down.
You have time, if you start now. You probably don't have much though, so start now!!!
I left it way to late last year and I got a D, my lowest grade in AS levels. I am retaking this year but I am making sure I actually go through it.
Don't make the same mistake as I did and do other work instead of the chemistry as you will just end up going to the exam without knowing anything at all.
There are LOTS of equations, so go ahead and learn them! I don't know if someone will really go through the effort to post them all.
If you need help on more specific things, feel free to post them.
Original post by TheNoobishKnight
Well first calm down.
You have time, if you start now. You probably don't have much though, so start now!!!
I left it way to late last year and I got a D, my lowest grade in AS levels. I am retaking this year but I am making sure I actually go through it.
Don't make the same mistake as I did and do other work instead of the chemistry as you will just end up going to the exam without knowing anything at all.
There are LOTS of equations, so go ahead and learn them! I don't know if someone will really go through the effort to post them all.
If you need help on more specific things, feel free to post them.
You have time, if you start now. You probably don't have much though, so start now!!!
I left it way to late last year and I got a D, my lowest grade in AS levels. I am retaking this year but I am making sure I actually go through it.
Don't make the same mistake as I did and do other work instead of the chemistry as you will just end up going to the exam without knowing anything at all.
There are LOTS of equations, so go ahead and learn them! I don't know if someone will really go through the effort to post them all.
If you need help on more specific things, feel free to post them.
Lol, sorry. It's mainly because I know nothing for all my subjects and I have three. So bye bye uni for me I guess. When did you begin for chemistry?
Original post by TheNoobishKnight
Well first calm down.
You have time, if you start now. You probably don't have much though, so start now!!!
I left it way to late last year and I got a D, my lowest grade in AS levels. I am retaking this year but I am making sure I actually go through it.
Don't make the same mistake as I did and do other work instead of the chemistry as you will just end up going to the exam without knowing anything at all.
There are LOTS of equations, so go ahead and learn them! I don't know if someone will really go through the effort to post them all.
If you need help on more specific things, feel free to post them.
You have time, if you start now. You probably don't have much though, so start now!!!
I left it way to late last year and I got a D, my lowest grade in AS levels. I am retaking this year but I am making sure I actually go through it.
Don't make the same mistake as I did and do other work instead of the chemistry as you will just end up going to the exam without knowing anything at all.
There are LOTS of equations, so go ahead and learn them! I don't know if someone will really go through the effort to post them all.
If you need help on more specific things, feel free to post them.
Wait re-taking? Why? If D was your lowest grade then why re-take the whole year again?
Original post by Cherry82
Wait re-taking? Why? If D was your lowest grade then why re-take the whole year again?
Trust me you got loads of days like 45 or something to revise for.it.
I am.just retaking the exams lol I'm gonna do my A2 too
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Does anyone have any ideas on how to prepare for isas, i have one next week for AQA
Original post by BeckyWarkup
Does anyone have any ideas on how to prepare for isas, i have one next week for AQA
Remember what you did for the experiment, try think of questions they could ask you. If you're an AS student, both ISA papers are simple papers with one or two tricky one markers but otherwise revise the relevant topics that you've been told, depends which ISA you're doing? AS or A2?
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