Q15 P Vapor at a pressure of 30.3渭迟聽... [FREE SOLUTION]

Chapter 18: Q15 P (page 456)

Vapor at a pressure of $30.3 渭迟$ bar from the solid compound pyrazine had a transmittance of 24.4% at a wavelength of 266nm in
a 3.00 - cm cell at 298K
Pyrazine
(a) Convert transmittance to absorbance.
(b) Convert pressure to concentration (mol/L) with the ideal gas law (Problem 1-18).
(c) Find the molar absorptivity of gaseous pyrazine at 266nm.

Short Answer

Expert verified

Absorbance is 0.613.
Pressure is $1.67 脳 10^{- 5} M^{- 1} c m^{- 1} .$ .
Molar absorptivity is $1.22 脳 10^{- 6} .$ .

Step by step solution

Absorbance.

Absorbance (A), also known as optical density (OD), is the quantity of light absorbed by a solution. Transmittance is the quantity of light that passes through a solution.

Calculation of Absorbance.

A = - log(T)

Therefore,

A = - log(0.244)

A = 0.613

Calculation of the concentration of gas related to pressure.

$c = \frac{n}{V}$

Also,

$c = \frac{p}{R 鈰� T} c = \frac{30.3 鈰� 10^{- 6} b a r}{0.08314 L 鈰� b a r / m o l 鈰� K 鈰� 298 K} c = 1.22 鈰� 10^{- 6} M$

The value of Molar absorbance.

As absorbance is

$A = 蔚鈰� c 鈰� b$

Therefore,

$蔚 = \frac{A}{c 鈰� b} 蔚 = \frac{0.613}{1.22 鈰� 10^{- 6} M 鈰� 3 c m} 蔚 = 1.67 鈰� 10^{5} M^{- 1} c m^{- 1}$

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Short Answer

Step by step solution

Absorbance.

Calculation of Absorbance.

Calculation of the concentration of gas related to pressure.

The value of Molar absorbance.

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