AS Chemistry- helping each other out!
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Original post by abzaa
Hey I need help, I hav my chemistry ISA coming up and I havnt revised for cause my mum passed away, can some plz help me on the ISA it's on titration any help would be really appreciated thanks, I'm will to exchange other info on empa for year 13
TSR Rules:
Practical exams in science subjects are taken by different groups of students across an extended period of time. This means that some people will have finished an exam that hasn't even been started by others. Along similar lines to the restrictions for written exams discussed above, we'll close and/or remove any threads requesting/disclosing specific details of practical exams. However, we realise that you may want to talk about the exams with others once you've completed them, and as such it's acceptable to discuss the practicals on a general level. For example, asking others about the difficulty of the exams as a whole should be fine in most cases. It's also acceptable to ask for general advice prior to sitting an exam, such as on how to draw graphs, or what words mean within questions.
Again, these rules apply to private messages as well as to posts on the public forums. Please see the Exam Discussion Rules page for more detailed information.
Original post by Hadiqa malik
Original post by anoymous1111
anyone done the qualitative on investigating reactions of salts and making solutions of salts?
Posted from TSR Mobile
Posted from TSR Mobile
TSR Rules:
Practical exams in science subjects are taken by different groups of students across an extended period of time. This means that some people will have finished an exam that hasn't even been started by others. Along similar lines to the restrictions for written exams discussed above, we'll close and/or remove any threads requesting/disclosing specific details of practical exams. However, we realise that you may want to talk about the exams with others once you've completed them, and as such it's acceptable to discuss the practicals on a general level. For example, asking others about the difficulty of the exams as a whole should be fine in most cases. It's also acceptable to ask for general advice prior to sitting an exam, such as on how to draw graphs, or what words mean within questions.
Again, these rules apply to private messages as well as to posts on the public forums. Please see the Exam Discussion Rules page for more detailed information.
Just a reminder for everyone, I'm not sure if this has been said already but I don't think anyone is allowed to share any ISA/EMPA (irregardless of exam board) on TSR.
Additionally, I don't believe anyone should be sharing the 2014 June paper (the most recent papers) on this thread or across the forum for chemistry (or any other subject for that matter either) as well.
I've already been PM'ed a few times for Edexcel ISA papers/June 2014 papers which are not allowed to shared on this forum.
Sharing those resources (whilst they are locked or not available on the exam boards website) could be classed as cheating which I'm sure that no one should be doing
Apologies if anyone takes any offence, I'm just saying it to prevent any cheating from occuring on TSR.
Additionally, I don't believe anyone should be sharing the 2014 June paper (the most recent papers) on this thread or across the forum for chemistry (or any other subject for that matter either) as well.
I've already been PM'ed a few times for Edexcel ISA papers/June 2014 papers which are not allowed to shared on this forum.
Sharing those resources (whilst they are locked or not available on the exam boards website) could be classed as cheating which I'm sure that no one should be doing
Apologies if anyone takes any offence, I'm just saying it to prevent any cheating from occuring on TSR.
Oooppss sorry won't happen again
Has anyone received the advance notice booklet for OCR B chemistry yet?
If so we could discuss possible questions (what our teacher think and what we think), I don't think it's a problem since it states "Candidates should be able to discuss the Advance Notice freely" on the booklet. Thanks!
Posted from TSR Mobile
If so we could discuss possible questions (what our teacher think and what we think), I don't think it's a problem since it states "Candidates should be able to discuss the Advance Notice freely" on the booklet. Thanks!
Posted from TSR Mobile
Anyone care to help me with displayed/structural formula
3-methylbutan-1-ol
Is the structural formula
CH3CH(CH3)CH2CH2OH
The next one is to draw out CH3CH3COCH(CH3)2
is that 2-methyl-pentan-3-one?
What does 3-oxobutanal look like?
3-methylbutan-1-ol
Is the structural formula
CH3CH(CH3)CH2CH2OH
The next one is to draw out CH3CH3COCH(CH3)2
is that 2-methyl-pentan-3-one?
What does 3-oxobutanal look like?
(edited 9 years ago)
When silicon tetrachloride is added to water, the following reactionoccurs:
SiCl4(l)+ 2H2O(l)SiO2(s)+ 4HCl(aq)
1.2g of impure silicon tetrachloride was dissolved in excess water, andthe resulting solution was made up to 250 cm3.A 25 cm3portion of the solution was then titrated against 0.10 moldm-3sodium hydroxide, and 18.7 cm3of the alkali were required. What was the percentage purity of thesilicon tetrachloride?
I've been stuck on this for a while now. Any help would be appreciated
SiCl4(l)+ 2H2O(l)SiO2(s)+ 4HCl(aq)
1.2g of impure silicon tetrachloride was dissolved in excess water, andthe resulting solution was made up to 250 cm3.A 25 cm3portion of the solution was then titrated against 0.10 moldm-3sodium hydroxide, and 18.7 cm3of the alkali were required. What was the percentage purity of thesilicon tetrachloride?
I've been stuck on this for a while now. Any help would be appreciated
Original post by Super199
Anyone care to help me with displayed/structural formula
3-methylbutan-1-ol
Is the structural formula
CH3CH(CH3)CH2CH2OH
The next one is to draw out CH3CH3COCH(CH3)2
is that 2-methyl-pentan-3-one?
What does 3-oxobutanal look like?
3-methylbutan-1-ol
Is the structural formula
CH3CH(CH3)CH2CH2OH
The next one is to draw out CH3CH3COCH(CH3)2
is that 2-methyl-pentan-3-one?
What does 3-oxobutanal look like?
you're right for the first two, 3-oxobutanal has the structural formula of CH3COCH2CHO
Original post by ThatMadClown
you're right for the first two, 3-oxobutanal has the structural formula of CH3COCH2CHO
What does oxo mean?
I have a few more if you don't mind checking.
2,2-diflourobutanoic acid.
CH3CH2C(F)2COOH
Not sure about 4-hydroxypentanoic acid
1-chlorobutan-2-one
CH2ClCOCH2CH3
Not sure about but-3-enal?
The next one is to name the thing. The structural formula is (CH3)2C(OH)CH2COOH
No idea how you name this.
It has an alcohol and a carboxylic acid?
Similar problem with CH2=CHCH2COOH
Which I put as But-1-eneoic acid
Another one CH3CH(OH)CH2COCH3
Which I don't even know how to display
Last one is CCl3COOH
1,1,1-trichloroanoic acid? haha if that exists.
Thanks for your help
Original post by TheGreatImposter
Has anyone received the advance notice booklet for OCR B chemistry yet?
If so we could discuss possible questions (what our teacher think and what we think), I don't think it's a problem since it states "Candidates should be able to discuss the Advance Notice freely" on the booklet. Thanks!
Posted from TSR Mobile
If so we could discuss possible questions (what our teacher think and what we think), I don't think it's a problem since it states "Candidates should be able to discuss the Advance Notice freely" on the booklet. Thanks!
Posted from TSR Mobile
Printed it today. I read it and thought something along the lines of "hmmm, I have no idea what to take from this."
Original post by Super199
What does oxo mean?
I have a few more if you don't mind checking.
2,2-diflourobutanoic acid.
CH3CH2C(F)2COOH
Not sure about 4-hydroxypentanoic acid
1-chlorobutan-2-one
CH2ClCOCH2CH3
Not sure about but-3-enal?
The next one is to name the thing. The structural formula is (CH3)2C(OH)CH2COOH
No idea how you name this.
It has an alcohol and a carboxylic acid?
Similar problem with CH2=CHCH2COOH
Which I put as But-1-eneoic acid
Another one CH3CH(OH)CH2COCH3
Which I don't even know how to display
Last one is CCl3COOH
1,1,1-trichloroanoic acid? haha if that exists.
Thanks for your help
I have a few more if you don't mind checking.
2,2-diflourobutanoic acid.
CH3CH2C(F)2COOH
Not sure about 4-hydroxypentanoic acid
1-chlorobutan-2-one
CH2ClCOCH2CH3
Not sure about but-3-enal?
The next one is to name the thing. The structural formula is (CH3)2C(OH)CH2COOH
No idea how you name this.
It has an alcohol and a carboxylic acid?
Similar problem with CH2=CHCH2COOH
Which I put as But-1-eneoic acid
Another one CH3CH(OH)CH2COCH3
Which I don't even know how to display
Last one is CCl3COOH
1,1,1-trichloroanoic acid? haha if that exists.
Thanks for your help
If a molecule has both ketone and aldehyde in it than you take the aldehyde C=O to be first priority meaning you count from that carbon and the ketone
C=O is given the suffix oxo-
4-hydroxypentanoic acid would be CH3CH(OH)CH2CH2COOH you count from the carbon in the carboxyl group
but-3-enal would be CH2=CHCH2CHO
the one where you have to name it would be 3-hydroxy-3-methylbutanoic acid
and lastly with the three chlorines that would be 2,2,2-trichloroethanoic acid
(edited 9 years ago)
Original post by panda14
Printed it today. I read it and thought something along the lines of "hmmm, I have no idea what to take from this."
Same but I think we're gonna through it in class soon and apparently it's worth 20 marks so I wanna make sure I smash them since they practically give it away
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Original post by panda14
A
Right can someone explain this question to me.
When you do the normal sum of products-sum of reactants it works.
But when I try with a Hess cycle I don't get the right answer. Anyone care to explain this to me?
When you do the normal sum of products-sum of reactants it works.
But when I try with a Hess cycle I don't get the right answer. Anyone care to explain this to me?
i have my AS Titration coming up soon. dont know how to prepare for it.
i had my AS thermal decomposition one today, didnt go so well. any tips on how to ace the titration isa
i had my AS thermal decomposition one today, didnt go so well. any tips on how to ace the titration isa
Original post by Ray Robinson
i have my AS Titration coming up soon. dont know how to prepare for it.
i had my AS thermal decomposition one today, didnt go so well. any tips on how to ace the titration isa
i had my AS thermal decomposition one today, didnt go so well. any tips on how to ace the titration isa
make sure you are so comfortable with all the stoichiometry and every kind of molar calculation. Make sure you're familiar with how to record your results, paying attention to consistent decimal places that are close in range and always the same number of decimal places, I advise 2 d.p . Also be familiar with the pH indicators and their colour changes. Make sure you're also comfortable with writing equations, and all types of acid base reactions. something to note is that even if your results are really inconsistent don't record them like that, so many people did that for some reason, I think there's a mark specifically for obtaining titres within 0.01cm3 range, but this is all based on OCR A by the way. Good luck!
AS student, I got 100% in my titration practical
(edited 9 years ago)
I really really really need help with an upcoming evaluative assessment retake, it make the difference of a whole grade for me. I'm AS OCR A, the assessment is on enthalpy change of combustion. I need to know what I should expecting... I got 100% in the other two im sooo nervous. Thank you so much
Original post by AyshaU
Like you said to me when we were talking about organic, how the hell can you love amount of substance, its an okay topic and I'm sure I've revised pretty much every question that is out there as I've started doing the same papers again. I know it comes in every paper and that scares me. I've just got bonding to cover and I have finished my CHEM1 revision. then onto CHEM2 (yay!!)
If iI' not being nosy can I just ask what other A-levels did you do and how much time did you spend on each of these per week.
If you don't want to answer I honestly would understand
If iI' not being nosy can I just ask what other A-levels did you do and how much time did you spend on each of these per week.
If you don't want to answer I honestly would understand
I guess the reason why I love Amount of Substances is because I love Maths and for me Amount of Substances is the best way I can exercise my Maths skills in a different subject.
No you're not being nosy at all
I student Maths, Physics and of course Chemistry.
I dropped English Literature at AS because I knew I would've neglected putting effort into it until the end of the year, even though I loved the subject, I didn't want to put that kind of stress on myself as I knew deep down I will always prioritise Maths and Sciences.
Uh outside school hours I'd spend at least 4.5 hours a day in general for school work but most of the time I use that time to do Maths homework because my teacher gives my class a crap load to do everyday
I cannot give you an approx figure as to how many hours I spend for each subject because how I use my time depends on how much work I get given from my teachers and whether I'll have enough time after to do my own independent revision.
But I think its safe to say most of my weekend is revision and consolidating time.
I hope that helps.
Now I hope I'm not being nosy by asking what other A - Levels you do.
Original post by Super199
Right can someone explain this question to me.
When you do the normal sum of products-sum of reactants it works.
But when I try with a Hess cycle I don't get the right answer. Anyone care to explain this to me?
When you do the normal sum of products-sum of reactants it works.
But when I try with a Hess cycle I don't get the right answer. Anyone care to explain this to me?
You're mistake in the picture is that you flipped both the arrows up, I believe you did this because they told you to find ΔHf so you must have assumed that after drawing the Combustion Hess' Cycle you'd then have to flip both sides up. But this implies that you're thinking all the values in the data are ΔHf values (if you were to take them as positive values).
Here's a tip when dealing with examination questions on Hess' cycles: if for example they ask you to find ΔHc of a certain reaction but the data they give you is ΔHf values then you must draw a Formation Hess' Cycle. But do not flip both arrows down just because they're asking for ΔHc, just flip the left arrow down so that the cycle can go in the right direction.
The picture above should help.
Your aim is to get ΔHc = -ΔHf2 + ΔHf1 OR ΔHc = ΔHf1 - ΔHf2
I hope that helps, let me know if you need any more help understanding this.
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