Colorimetry question help (1 Viewer)

[Run hard@thehsc]

How would you go about solving this question? thanks

 

[jazz519]

AAS, colourimetry, UV-vis questions are all generally solved in a similar way because the methods all involve using a calibration curve made from standard solutions

First use the graph. Absorbance 0.6105 ==> c(Fe3+) = 55 x 10^-6 mol/L
This is just by tracing across from y-axis to graph to x-axis

c = n/v
n(Fe3+) = cv
n(Fe3+) = (55x10^-6)(0.200)
n(Fe3+) = 1.1 x 10^-5 moles

n = m/MM
m(Fe3+) = n x MM
m(Fe3+) = (1.1 x 10^-5)(55.85)
m(Fe3+) = 6.14 x 10^-4 g

 

[Run hard@thehsc]

Oh ok got it thanks!

 

[Chan360]

how do you convert µmol/l to mol/l please? I noticed you multiplied it by 10^-6, is that the conversion?

 

[jazz519]

how do you convert µmol/l to mol/l please? I noticed you multiplied it by 10^-6, is that the conversion?

Yes that is the conversion

 

[Chan360]

Yes that is the conversion

thank you!

 

[jazz519]

Why did you times the 55 by 10^-6
When I read it off the graph it just says 55

Look at the unit it's not mol/L

It is written as μmol/L

μ = 10^-6

It's same thing as if you wrote 5 mg. You would need to do 5 x 10^-3 g.

m = milli = 10^-3
μ = micro = 10^-6