A 0,0000229 M sample of Compound X in a solvent has an absorbance of 0.241 at 52

Question

A 0,0000229 M sample of Compound X in a solvent has an absorbance of 0.241 at 528 nm in a 1.000-cm cuvet. The solvent alone has an absorbance of 0.066. What is the molar absorptivity of Compound X? Number A different sample of Compound X in the same solvent has an absorbance of 0.529 at 528 nm when measured with the same cuvet. What is the concentration of this second sample? Number mol X Previous sive Up & View Solution (2) Check Answer 0 Next HEI sbout us careers priuacy policy terms of use contact us helo

Explanation / Answer

To solve this problem, we have to use Beer's Law.

A=lc

Where,
A = Absorbance
= molar absorptivity or molar extinction coefficient
l = path length
c = concentration

Give;
A = 0.241; but there is also contribution of absorbance from the solvent A(s) = 0.066
Therefore,
the absorbance of compound X is : A(x) = A-A(S)
                                       = 0.241 - 0.066
                                       = 0.175
= ?
l = 1 cm
c = 0.000029 M
Therefore,the molar absorptivity of compoundX is:
= A/lc
= 0.175 / 1cm.0.000029 M
= 6034 M-1 cm-1

In another sample of Compound X, the absorbance is 0.529 measured.
A(x) = A - A(s)
   = 0.529 -0.066
   = 0.463
  
Therefore, the concentration C = A/l
                               = 0.463/6034 M-1 cm-1 x 1 cm
                               = 0.0000767 M
                               = 0.0000767 mol of X/L

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