nomchomchikapompom
New Member
- Joined
- Oct 8, 2014
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- HSC
- 2015
So the question is :
Discuss the validity and reliability of your results and conclusions.
basically I did an experiment to identify the unknown ion present in 3 different samples.
my results:
I concluded that Pb^2+ was present in one of the samples because it formed a white precipitate with HCl, NaOH and H2SO4
in the other sample PO4^3- was present cause it formed a yellow precipitate it AgNO3 but then the precipitate dissolved when HNO3 was added
and the last sample, is said carbonate ions were present because it formed bubbles with the addition of HCl and HNO3 (shows CO2 release), and also formed a white precipitate with addition of AgNO3 and then the precipitate dissolved with HNO3 addition.
so like i don't know what i'm doing basically, i wrote so much haha and yea, could someone just check and tell me what u'm suppose to do ( it's worth 5 marks)
+ didn't know wether to say it's invalid to assume e.g. lead was present cause it could've been silver but silver isn't part of the syllabus, so do i say that or..?
anyway here's what i wrote (sorry for horrible grammar
)
Validity:
The extent to which the processes and resultant data measure what was intended.
Does my procedure experiment actually test the hypothesis that I want it to? Have all variables been identified and controlled?
My aim was to deduce the ions present in samples “D’, ‘F’ an ‘K’. The results achieved this as well as corresponding with the theory of the solubility rules. All my controlled variables were kept constant and for that reason my result were valid.
Sample ‘ X ‘ formed a white precipitate with HCl and according to the solubility rules, the ion in sample ‘X’ was the lead ion, answering my aim in finding the ion. However although more tests where held to confirm the presence of lead such as the NaOH and the H2SO4 which both formed a white precipitate with sample ‘X’, the substance that formed a white precipitate with HCl could’ve been silver or mercury as they both form a white precipitate with HCl, NaOH and H2SO4. To validate our statement that the ions present were lead ions and this result wasn’t just an assumption, add iodide ions to sample ‘X’ and if a yellow precipitate forms, then it can be concluded that lead ions were present, this would make the results valid.
The conclusion that phosphate is the ion present in ‘sample x’ was shown in the formation of a yellow precipitate with silver ions, and because it dissolved with nitric acid, it further highlighted the presence of phosphate ions, however other ions may also react in this way, so to validate our results we can confirm the presence of the phosphate ion by reacting it with ammonium molybdate to form a yellow precipitate.
Also my results that CO3^2- ions were present in sample ‘X’ were valid as not only did it test positive when it formed a white precipitate with Ag^+ and then the precipitate dissolved with the addition of nitric and HCl formed bubbles (indicating release of CO2 gas), a trait that only carbonate ions would produce when reacting with an acid. But it’s presence was further confirmed with the separate addition of HCl and then nitric acid that formed bubbles (indicating release of CO2 gas), a trait that only carbonate ions would produce when reacting with an acid. However to be able to conclusively confirm that CO3^- were present, it should form a white precipitate with the addition of BaCl or Limewater.
Reliability:
The degree with which repeated observation and/or measurements taken under identical circumstances will yield the same results.
Have I tested with repetition?
For:
-Repeated twice with consistent results
Against:
The more times an experiment is repeated, the more anomalies stick out and can be discounted. Too check for anomalies and to show that the results weren't by luck/random. If you repeat it many times then the data is considered more reliable as the chance of it all be down to luck/random is reduced Repetition a third time would provide concrete results that would show that no matter how much repeated, the same observations would’ve been made and the observations were not by just chance.
Discuss the validity and reliability of your results and conclusions.
basically I did an experiment to identify the unknown ion present in 3 different samples.
my results:
I concluded that Pb^2+ was present in one of the samples because it formed a white precipitate with HCl, NaOH and H2SO4
in the other sample PO4^3- was present cause it formed a yellow precipitate it AgNO3 but then the precipitate dissolved when HNO3 was added
and the last sample, is said carbonate ions were present because it formed bubbles with the addition of HCl and HNO3 (shows CO2 release), and also formed a white precipitate with addition of AgNO3 and then the precipitate dissolved with HNO3 addition.
so like i don't know what i'm doing basically, i wrote so much haha and yea, could someone just check and tell me what u'm suppose to do ( it's worth 5 marks)
+ didn't know wether to say it's invalid to assume e.g. lead was present cause it could've been silver but silver isn't part of the syllabus, so do i say that or..?
anyway here's what i wrote (sorry for horrible grammar
)Validity:
The extent to which the processes and resultant data measure what was intended.
Does my procedure experiment actually test the hypothesis that I want it to? Have all variables been identified and controlled?
My aim was to deduce the ions present in samples “D’, ‘F’ an ‘K’. The results achieved this as well as corresponding with the theory of the solubility rules. All my controlled variables were kept constant and for that reason my result were valid.
Sample ‘ X ‘ formed a white precipitate with HCl and according to the solubility rules, the ion in sample ‘X’ was the lead ion, answering my aim in finding the ion. However although more tests where held to confirm the presence of lead such as the NaOH and the H2SO4 which both formed a white precipitate with sample ‘X’, the substance that formed a white precipitate with HCl could’ve been silver or mercury as they both form a white precipitate with HCl, NaOH and H2SO4. To validate our statement that the ions present were lead ions and this result wasn’t just an assumption, add iodide ions to sample ‘X’ and if a yellow precipitate forms, then it can be concluded that lead ions were present, this would make the results valid.
The conclusion that phosphate is the ion present in ‘sample x’ was shown in the formation of a yellow precipitate with silver ions, and because it dissolved with nitric acid, it further highlighted the presence of phosphate ions, however other ions may also react in this way, so to validate our results we can confirm the presence of the phosphate ion by reacting it with ammonium molybdate to form a yellow precipitate.
Also my results that CO3^2- ions were present in sample ‘X’ were valid as not only did it test positive when it formed a white precipitate with Ag^+ and then the precipitate dissolved with the addition of nitric and HCl formed bubbles (indicating release of CO2 gas), a trait that only carbonate ions would produce when reacting with an acid. But it’s presence was further confirmed with the separate addition of HCl and then nitric acid that formed bubbles (indicating release of CO2 gas), a trait that only carbonate ions would produce when reacting with an acid. However to be able to conclusively confirm that CO3^- were present, it should form a white precipitate with the addition of BaCl or Limewater.
Reliability:
The degree with which repeated observation and/or measurements taken under identical circumstances will yield the same results.
Have I tested with repetition?
For:
-Repeated twice with consistent results
Against:
The more times an experiment is repeated, the more anomalies stick out and can be discounted. Too check for anomalies and to show that the results weren't by luck/random. If you repeat it many times then the data is considered more reliable as the chance of it all be down to luck/random is reduced Repetition a third time would provide concrete results that would show that no matter how much repeated, the same observations would’ve been made and the observations were not by just chance.
