Yr 12. Determination of Keq by Colorimetry

[macca]

Hi Brains trust,

Person Chemistry 12 prac.5.4

Is anyone having a win doing this practical? This is the second year we are having no luck with results.

Thanks in advance

[kimmy]

iv just been given this prac to get ready and trying to work out the chemicals at the moment.

[macca]

Hi Kimmy

Yep a real nightmare. This year, different teacher has tried a variation and is getting some results although not the higher readings that were sort.

Using 0.1M HNO3
0.5M KSCN
0.0001M Fe(NO3)3

0.0025M KSCN
0.0025M Fe(NO3)3

[kimmy]

Thank you, ill let you know how we get on next week.

[bigmack]

We just did it .Chem teacher used an old book they used to do it 20 years ago .

0.2M Fe(NO)3
0.002M KSCN

He said it worked a teat . I wonder if your books have typos in them and the Molarities are back to front

[Merilyn1]

My Chem teacher uses 5ml each of 0.2M Ferric Nitrate and 0.2M of KSCN. Seems happy with that.

[ctzavellas]

Hey bigmac,

Which textbook is your chem teacher using, as we too are getting some weird results? Could you please find out for me.
Thnks

Carlie

[bigmack]

Hey bigmac,

Which textbook is your chem teacher using, as we too are getting some weird results? Could you please find out for me.
Thnks

Carlie

Hi Carlie
It's an old text book called Chemical Science ,Laboratory Manual ,Carswell.
We have both the student version and the teachers version which has answers in it .


out of interest I was telling my Chem teacher that some were having issues with it . He pointed to the answers obtained in the teachers version of the book and suggested that perhaps the teachers were expecting exact number constant on each test whereas in reality there is a spread of answers that are around the constant value expected .

Here's a cropped screen shot of the pdf copy of the teachers version of the book .

Equalibrium.png

Equalibrium teachers answers.pdf

Equalibrium.pdf

[macca]

Thanks

[ctzavellas]

Hey Macca,

Did you guys use both the method of matching the color by eye and colorimeter for this prac?

Carlie

[ctzavellas]

Hey Macca,

Did you guys use both the method of matching the color by eye and colorimeter for this prac?

Carlie

[macca]

Yes we did, they are going to give that old method above ago next year. Think just ended up speculating on what the results should have bwen.