Any questions you may have can be asked here provided they would benefit each topic. I will not tell you specific details about milk going off for example but I will provide general feedback that will benefit everyone.
Hi Mr H, For our EEI we need to investigate what acids are present in white wine, and how the acid content might change. Does this mean we need to experimentally change the acid content ourselves, or can we simply compare the acidity different types of wine?
Firstly to make different wines your independent variable in itself is too broad in scope for you to investigate and find reasonable conclusions. There is no purpose in deliberately changing the acid content.
In our logbooks, do we basically write the calculations (eg. calculating the mass of KHP), a brief reflection on the experiment and the refinement of task? Do we need to write the procedure for each experiment as well?
you do not need to do everything twice. The only calculations needed in your logbook are those that help your ongoing experimental work. This would definitely include calculations for standardising solutions but not calculations for the final acid content. Your logbook should contain your thoughts as you are directing and reflecting on your days work. Your draft report and final report are your response to the overall task. You might for instance write down what you need to research in your logbook and you can include research notes in your logbook but it needs to be dated. Your report then contains the organised summary of your research. A plan of your report should be in your logbook. Your logbook should direct your report. Hope this helps.
Hi Mr Haliczer, just a quick question about my EEI, if we want to leave the soda water for 1 and 2 hours after it has been opened, how can we time that with lessons? If a bottle is opened in a single lesson or even a double we won't have enough time to titrate after the time intervals. What should we do? Louise
the calculations so far appear correct. Carbon dioxide dissolves in water to form carbonic acid which is a diprotic acid. 2 moles of NaOH are needed to neutralise one mole of carbonic acid.
Hi Mr H, for my standardisation calculations i got a very different answer to Theo, could you just check my working to make sure I am doing the right thing?? 1. Calculate the mass of KHP required to prepare a solution of 0.1M in a 250mL flask Calculate the formula mass of the substance KHP = KOOCC6H4COOH (KC8H5O4) Fr (KHP) = 39.098 + (8 x 12.011) + (5 x 1.008) + (4 x 15.999) = 204.222 Calculate the number of moles required n = C x V = 0.1 x 0.25 =0.025 mol Calculate the mass of substance required m = Fr x n =204.222 x 0.025 = 5.106g
2. Calculate concentration of NaOH solution Write formula for equation KC8H5O4 + NaOH KC8H4O4Na + H2O KHP + NaOH KP + H2O Calculate the number of moles of KHP in 25 mL solution n(KHP) = C x V =0.100 x 0.025 =0.0025 mol Calculate number of moles of NaOH solution n(NaOH) = n(KHP) =0.0025 mol Calculate concentration of NaOH solution used C(NaOH) = n/V =0.0025/0.01885 =0.133M Thanks, Louise
it appears you have used your theoretic amount of KHP in your calculations. Did you really weigh 5.106 g (the balance isn't accurate to that amount). Are you certain that your pipettes were 25ml and not 20ml as this might give you an artificially high value.
1. Does the data analysis section just include error analysis and any calculations we used?
2. How detailed should we be in our procedure? Should we mention rinsing equipment and such?
3. Given that group members have individually refined their procedure, do they need to discuss their changes with their partner and have each submit the exact same procedure?
4. Can we exclude rough titrations from our results section?
1. the data analysis section has a KCU section an IP section and an EC section. The KCU section is a mark for your ability to use correct calculations with all working shown to find the concentration of acid molecules and the degree of error with clear working and justification.The IP section of data analysis is how you interpret your results including identifying trends etc and the source of errors and anomolies. In EC, there are two unrelated expectations. First to use researched theory as elaborated in the introduction to provide reasons for the trends and anomolies and secondly to evaluate your laboratory procedure with justification.
2. In your procedure you should not be repetitive by mentioning every time you rinsed equipment. This could be a separate subheading perhaps with 1 - 2 sentences?
3. Your procedures ought to be indentical in meaning (in theory) but your own words. Do not paraphrase or copy from each other.
4. Rough titrations should be included in your results but with clear jsutification excluded from calculations for obvious reasons.
Mr. H. Do we need to have an abstract for the prac write up, or is it not required. Also, we put all the calcutions in the appendix but which calculations do we put in the analysis of the results? Thanks Heaps.
Ps. Please check this regularly i'll probably ask stuff on the weekend.
I don't believe an abstract is necessary but if you use one you need to do it properly. The analysis of results should demonstrate clearly how you performed your calculations but should only contain an example of one complete calculation with all working. All calculations other than this ought to be referred to as an attached appendix.
After we have calculated the concentration of the acid in our substance, I was wondering if it was necessary/appropriate to convert to a percentage composition? If so, could you advise on the method for this? Would it be mass/volume?
Percentage composition is only useful if you were relating this to the packaging. Use the chapter in your textbook on concentrations to be sure you have the same terms as the labelled contents.
Hi Mr H, When I am calculating the concentration of my soda water solution, and use the equation: 2NaOH + H2CO3 = Na2CO3 + 2 H2O, will the molar ratio be 2NaOH:1(H2CO3)??
Hi Mr H, I'm confused about how we figure out the concnetration of our solution from the average titration volume. What are the steps involved? Thanks!! :)
Hi Mr Haliczer, I was just wondering if it is necessary for us to re write the risks and controls for our experiment, or can we just refer to the ones we wrote in our research plan at the end of last term?? Louise
:) From the average volume & concentration of NaOH you can work out moles of NaOH. Now use the stoichiometric ratio to determine moles of acid. As you will have 20mL of acid the concentration is easily worked out.
the risk assessment is covered provided you did this correctly in the original sheet. If you have needed to make ammendments then add these to your report. Controls are necessary in your report assuming you don't mean controlling risk. If you mean controlling variables then this is an essential part of your report.
On the wine bottle, it mentions the percentage of alcohol content in the wine only; not the acid content. How do we 'change' the alcohol percentage into the acidity percentage?
Hi Anju, p305 of textbook is the only hint I will give on this one. You would need to find the density of the acids which may be possible online to determine the Molarity.
26 comments:
Acid concentration is only proportional to pH if the acid is a strong acid!
yes
Hi Mr H,
For our EEI we need to investigate what acids are present in white wine, and how the acid content might change. Does this mean we need to experimentally change the acid content ourselves, or can we simply compare the acidity different types of wine?
Firstly to make different wines your independent variable in itself is too broad in scope for you to investigate and find reasonable conclusions. There is no purpose in deliberately changing the acid content.
In our logbooks, do we basically write the calculations (eg. calculating the mass of KHP), a brief reflection on the experiment and the refinement of task? Do we need to write the procedure for each experiment as well?
Hi Anju,
you do not need to do everything twice. The only calculations needed in your logbook are those that help your ongoing experimental work. This would definitely include calculations for standardising solutions but not calculations for the final acid content. Your logbook should contain your thoughts as you are directing and reflecting on your days work. Your draft report and final report are your response to the overall task. You might for instance write down what you need to research in your logbook and you can include research notes in your logbook but it needs to be dated. Your report then contains the organised summary of your research. A plan of your report should be in your logbook. Your logbook should direct your report. Hope this helps.
Hi Mr Haliczer, just a quick question about my EEI, if we want to leave the soda water for 1 and 2 hours after it has been opened, how can we time that with lessons? If a bottle is opened in a single lesson or even a double we won't have enough time to titrate after the time intervals. What should we do?
Louise
Hi Louise,
You can plan to have the bottles opened earlier than the class. See me before the class to get the lab opened so that you can open the bottle.
Mr H
Sir,
I am not to certain if this is correct, or that I am doing this correctly.
Average Titration volume = 20.715 ml.
5.10 g of KHP dissolved in 250ml water.
n (KHP) = m/M
= 0.02497 mol
C (KHP) = n/V
=0.02497/0.0250
=0.099 M
n (KHP Solution) = CV
= 0.099 X 0.02
= 1.98 X 10-3
1:1
n(KHP) = n (NaOH)
n(NaOH0) = 1.98 X 10-3
C (NaOH) = 1.98 X 10-3 / 0.020715
=0.095 M of NaOH.
also, I reasearched a small bit on malolactic fermentation.
could you please explain how CO2 could effect acid content?
Thankyou Theo. Bell
Hi Theo,
the calculations so far appear correct. Carbon dioxide dissolves in water to form carbonic acid which is a diprotic acid. 2 moles of NaOH are needed to neutralise one mole of carbonic acid.
regards,
Mr H
Hi Mr H, for my standardisation calculations i got a very different answer to Theo, could you just check my working to make sure I am doing the right thing??
1. Calculate the mass of KHP required to prepare a solution of 0.1M in a 250mL flask
Calculate the formula mass of the substance
KHP = KOOCC6H4COOH (KC8H5O4)
Fr (KHP) = 39.098 + (8 x 12.011) + (5 x 1.008) + (4 x 15.999)
= 204.222
Calculate the number of moles required
n = C x V
= 0.1 x 0.25
=0.025 mol
Calculate the mass of substance required
m = Fr x n
=204.222 x 0.025
= 5.106g
2. Calculate concentration of NaOH solution
Write formula for equation
KC8H5O4 + NaOH KC8H4O4Na + H2O
KHP + NaOH KP + H2O
Calculate the number of moles of KHP in 25 mL solution
n(KHP) = C x V
=0.100 x 0.025
=0.0025 mol
Calculate number of moles of NaOH solution
n(NaOH) = n(KHP)
=0.0025 mol
Calculate concentration of NaOH solution used
C(NaOH) = n/V
=0.0025/0.01885
=0.133M
Thanks, Louise
Hi Louise,
it appears you have used your theoretic amount of KHP in your calculations. Did you really weigh 5.106 g (the balance isn't accurate to that amount). Are you certain that your pipettes were 25ml and not 20ml as this might give you an artificially high value.
Hi Mr H, I have a few questions:
1. Does the data analysis section just include error analysis and any calculations we used?
2. How detailed should we be in our procedure? Should we mention rinsing equipment and such?
3. Given that group members have individually refined their procedure, do they need to discuss their changes with their partner and have each submit the exact same procedure?
4. Can we exclude rough titrations from our results section?
Hi Hannah,
1. the data analysis section has a KCU section an IP section and an EC section. The KCU section is a mark for your ability to use correct calculations with all working shown to find the concentration of acid molecules and the degree of error with clear working and justification.The IP section of data analysis is how you interpret your results including identifying trends etc and the source of errors and anomolies. In EC, there are two unrelated expectations. First to use researched theory as elaborated in the introduction to provide reasons for the trends and anomolies and secondly to evaluate your laboratory procedure with justification.
2. In your procedure you should not be repetitive by mentioning every time you rinsed equipment. This could be a separate subheading perhaps with 1 - 2 sentences?
3. Your procedures ought to be indentical in meaning (in theory) but your own words. Do not paraphrase or copy from each other.
4. Rough titrations should be included in your results but with clear jsutification excluded from calculations for obvious reasons.
Hi hi,
Mr. H. Do we need to have an abstract for the prac write up, or is it not required. Also, we put all the calcutions in the appendix but which calculations do we put in the analysis of the results? Thanks Heaps.
Ps. Please check this regularly i'll probably ask stuff on the weekend.
I don't believe an abstract is necessary but if you use one you need to do it properly. The analysis of results should demonstrate clearly how you performed your calculations but should only contain an example of one complete calculation with all working. All calculations other than this ought to be referred to as an attached appendix.
Hi sir,
After we have calculated the concentration of the acid in our substance, I was wondering if it was necessary/appropriate to convert to a percentage composition? If so, could you advise on the method for this? Would it be mass/volume?
Thanks
Percentage composition is only useful if you were relating this to the packaging. Use the chapter in your textbook on concentrations to be sure you have the same terms as the labelled contents.
Hi Mr H,
When I am calculating the concentration of my soda water solution, and use the equation: 2NaOH + H2CO3 = Na2CO3 + 2 H2O, will the molar ratio be 2NaOH:1(H2CO3)??
Hi Mr H, I'm confused about how we figure out the concnetration of our solution from the average titration volume. What are the steps involved?
Thanks!! :)
Hi Mr Haliczer, I was just wondering if it is necessary for us to re write the risks and controls for our experiment, or can we just refer to the ones we wrote in our research plan at the end of last term??
Louise
Molar ratio question for soda water - there are 2 moles of NaOH required to neutralise 1 mole of H2CO3 to get to the phenolphthalein end point.
:) From the average volume & concentration of NaOH you can work out moles of NaOH. Now use the stoichiometric ratio to determine moles of acid. As you will have 20mL of acid the concentration is easily worked out.
Hi Louise,
the risk assessment is covered provided you did this correctly in the original sheet. If you have needed to make ammendments then add these to your report. Controls are necessary in your report assuming you don't mean controlling risk. If you mean controlling variables then this is an essential part of your report.
Hi Mr H,
On the wine bottle, it mentions the percentage of alcohol content in the wine only; not the acid content. How do we 'change' the alcohol percentage into the acidity percentage?
Hi Anju, p305 of textbook is the only hint I will give on this one. You would need to find the density of the acids which may be possible online to determine the Molarity.
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