Table 3: Molar absorptivities of HIn and In - and the absorbances of the unknown
ID: 304704 • Letter: T
Question
Table 3: Molar absorptivities of HIn and In- and the absorbances of the unknown sample
Wavelength
eacid form,
ebase form,
Absorbance of unknown,
la
17693.69369
2630.630631
0.437
lb
72.072072707
30666.66667
0.101
b= 1cm
Find [ln-]/[Hln] ratio.
Can you use the method that finds ln- by itself then insert that into the second equation to find the real Hln?
Table 3: Molar absorptivities of HIn and In- and the absorbances of the unknown sample
Wavelength
eacid form,
ebase form,
Absorbance of unknown,
la
17693.69369
2630.630631
0.437
lb
72.072072707
30666.66667
0.101
Explanation / Answer
Formula: A = ebc, where 'c' is the concentration of absorbing medium
For HIn:
0.437 = 17693.69369 M-1cm-1 * 1 cm * [HIn]
i.e. [HIn] = 0.437/17693.69369 M
i.e. [HIn] = 2.47*10-5 M
For In-:
0.101 = 72.072072707 M-1cm-1 * 1 cm * [In-]
i.e. [In-] = 0.101/72.072072707 M
i.e. [In-] = 1.4*10-3 M
Now, [In-]/[HIn] = 1.4*10-3 M/2.47*10-5 M = 56.7
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