Beer\'s Law Lab You must show your work. No work = no credit. A 0.070 M solution

Question

Beer's Law Lab You must show your work. No work = no credit. A 0.070 M solution has an absorbance or A = 0.689. If a 1.00 cm path length w as used, calculate the molar absorptivity constant (epsilon) for this solution. Be sure to include the units! Use the equation for the best fit line for the plot of below to calculate the concentration of the standard that has an absorbance value of 0.312. In the heat of vaporization lab you plotted in Pvap vs 1/T (K). Using the data in the plot where In P is In P_vap determine the heat of vaporization for this liquid.

Explanation / Answer

A)

Apply Beer's LAw:

A = e*l*c

A = absorption, 0.689; e = molar absorptivity, l = 1 cm path length, and C = concentraiton 0.07 M

so

e = A/(l*C) = (0.689)/(1*0.07) = 9.84285 cm^-1 * M^-1

b)

calcualte concentration of standard of A= 0.312

so..

0.312 = 34.27*x + 0.0032

x = (0.312 -0.0032) /(34.27) = 0.0090107 M

Q3.

for a ln(P) vs- 1/T graph

the slope = -H/R

so

H = R*slope

H = 8.314*3777

H = 31401.978 J/mol

H = 31.4 kJ/mol

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