Concentration factor on rate of reaction..What is your concentration

[[Announcements] [Introduce Yourself] [ICT] [Prasekolah] [LINUS] [KSSR] [UPSR] [PMR] [SPM] [STPM] [School] [Classroom] [Clubs & Uniformed Bodies] [JPN] [SPA] [SICT] [SPP] [SPS] [SPPK] [SPSPK] [SPI] [SPsK] [JNJK] [PPD] [Program] [Computer & Internet] [Let's Hear It From You] [Membergroup]]

[Announcements] [Introduce Yourself] [ICT] [Prasekolah] [LINUS] [KSSR] [UPSR] [PMR] [SPM] [STPM] [School] [Classroom] [Clubs & Uniformed Bodies] [JPN] [SPA] [SICT] [SPP] [SPS] [SPPK] [SPSPK] [SPI] [SPsK] [JNJK] [PPD] [Program] [Computer & Internet] [Let's Hear It From You] [Membergroup]

[Lim Tze Khai]

Eksperiment 1.2 in the Chemistry F5 practical book.

How did you calculate the concentration of Na₂S₂O₃?

From the teachers that i met, i can classify the calculation method into two group?

Both group calculate the concentration by dilution method but

Group 1, use the final volume as 45 cm³ without consider the 5 cm₃ of acid added.

Group 2, use the final volume as 50 cm³ by adding 5 cm₃ of the acid as shown in the text book.

Everyone has their reason but which one should be teach to our students so that they can answer correct in the exam???

[Liew Hui Lee]

The calculation of the concentration should use 45cm³ as the final total volume.  The dilution is considered as chemicals / substances diluted by distilled water and not the others solutions / liquids ie. acid.  In this experiment, when 5 cm³ of HCl acid is added, actually a chemical reaction occurs to form new products.  That is not the dilution.

[James Bengak Anak Kumpang]

I agree with you, Liew Hui Lee. How about the other? Mr Jong...

[Jong Kah Yin]

Personally, i think it is not appropriate to include the volume of acid added into the total volume after dilution. We are adding water to dilute the sodium thiosulphate solution and that is the concentration of the solution before reacting with sulphuric acid.
The old text book followed the above method in the calculation of the concentration of sodium thiosulphate solution. Maybe there are other teachers who do not @buy@ this thought should help to enlighten us.

[Lim Tze Khai]

I think Pentaksir-pentaksir PEKA + GC so discuss on this problem and give us a solid answer on which matter to teach to our students.
___________________________________________________________

Acid is an aqueous solution - solute + water

When acid added to Na2S2O3 and before they react, dilution of Na2S2O3 by water in acid does occur.

The is the reason given by the group 2.

[Tay Guan Piang]

I think Pentaksir-pentaksir PEKA + GC so discuss on this problem and give us a solid answer on which matter to teach to our students.
___________________________________________________________

Acid is an aqueous solution - solute + water

When acid added to Na2S2O3 and before they react, dilution of Na2S2O3 by water in acid does occur.

The is the reason given by the group 2.

I agree with you, Mr.Lim. I think this matter should be highlighted to everyone here as when i read through the experiment in Practical Book, i found another problem that may be cause misconception to teachers and students. Please refer page.12 Practical book:

1. Calculate the concentration of sodium thiosulphate, Na₂S₂O₃ solution in the reacting mixture before the reaction starts in each of the sets I to V, using the relationship M₁V₁ = M₂V₂.

M₁ = Concentration of sodium thiosulphate, Na₂S₂O₃ solution used before mixing (0.2 mol dm^-3)
V₁ = Volume of sodium thiosulphate, Na₂S₂O₃ solution used before mixing
M₂ = Concentration of sodium thiosulphate, Na₂S₂O₃ solution after mixing but before the reaction starts
V₂ = Total volume of the reacting mixture (50 cm³)

well, if according to the instruction provided in the above question (Practical book), then the Group 2 approach will be much preferred.

[Hamidah Ripin]

I agree with you, Mr.Lim. I think this matter should be highlighted to everyone here as when i read through the experiment in Practical Book, i found another problem that may be cause misconception to teachers and students. Please refer page.12 Practical book:

1. Calculate the concentration of sodium thiosulphate, Na₂S₂O₃ solution in the reacting mixture before the reaction starts in each of the sets I to V, using the relationship M₁V₁ = M₂V₂.

M₁ = Concentration of sodium thiosulphate, Na₂S₂O₃ solution used before mixing (0.2 mol dm^-3)
V₁ = Volume of sodium thiosulphate, Na₂S₂O₃ solution used before mixing
M₂ = Concentration of sodium thiosulphate, Na₂S₂O₃ solution after mixing but before the reaction starts
V₂ = Total volume of the reacting mixture (50 cm³)

well, if according to the instruction provided in the above question (Practical book), then the Group 2 approach will be much preferred.

my students also confuse with this question...

[Tay Guan Piang]

my students also confuse with this question...

Not only students confuse, me as teacher also headache because of this, Cgu Hamidah. A lot of arguments between me and students, and i told them to hold the argument as i discuss with all the Chemistry teachers through this portal. Perhaps we can seek advices from Mr.Jong, Mr. Lim or other experienced teachers.   

[Jong Kah Yin]

The present practical book used the Group 2 approach. For argument sake, which one occurs first? Dilution then reaction or the other way around? That 5 cm³ of acid will not very much affect the concentration of sodium thiosulphate solution as the later has a much bigger volume than the acid. That is my line of thinking.

[Lim Tze Khai]

The problem here is know what we think of?

But which method should students apply to answer the question in SPM if being ask...

Text book should be use as a standard material in teaching as it is being use by the whole nation students and we are ask to follow the text book for any argument.

How is others opinion???

That is what i am asking for this matter to be discuss by the GC and make correction to the text book if necessary..

[Tay Guan Piang]

The problem here is know what we think of?

But which method should students apply to answer the question in SPM if being ask...

Text book should be use as a standard material in teaching as it is being use by the whole nation students and we are ask to follow the text book for any argument.

How is others opinion???

That is what i am asking for this matter to be discuss by the GC and make correction to the text book if necessary..

Yup, i agree with you, Mr. Lim. Should we clarify this mistake before it goes deeper. Otherwise students will keep on following the same misconception in their future study.

[Mohamad Rizuan Bin Sarbini]

this process will vary if you stir the dilution,

pH value in the solution = (use pH meter)

 

[Lim Tze Khai]

this process will vary if you stir the dilution,

pH value in the solution = (use pH meter)

 

Please explain more .....

why pH value ? in this experiment

please clarify.
10s

[Sim Thiam Huat]

ya ,
i'm also puzzled with this. may be all the GCs nationwide can discuss and come to a common conclusion for the benefit of everybody. 1 malaysia, pelajar diutamakan, pencapaian didahulukan !

Advanced search