Chemistry Worksheets With Answers (Page 3 of 5) in pdf

Chemistry Worksheets With Answers Page 3

Chem 338 Homework #6

6.16) At 300 K, the vapor pressure of dilute solutions of HCl in liquid GeCl4 as as

follows:

x(HCl)

0.005

0.012

0.019

p/kPa

32.0

76.9

121.8

Show that the solution obeys Henry’s law in this range of mole fractions and

calculate the Henry’s law constant at 300 K.

Henry’s law is p

= x

, where B = HCl in this case. If this solution obeys

Henry’s law in this mole fraction range, a plot of mole fraction versus vapor

pressure should yield a straight line with a slope given by the Henry’s law constant.

A more accurate method is to fit the data to a quadratic polynomial in x and

evaluate the first derivative at x=0 (this yields the tangent to the curve). Both

methods are shown in the plot below and yield essentially the same result. From the

linear fit, one obtains K=6411 kPa or 6.4 MPa, while the 1

derivative of the

quadratic yields 6402 kPa or also 6.4 MPa. Certainly Henry’s law is obeyed for

these concentration ranges.

y = -0.025485 + 6411.2x R= 1

140

Y = M0 + M1*x + ... M8*x

+ M9*x

120

M 0

-0.0067728

M 1

6402.2

M 2

471.08

100

0.005

0.01

0.015

0.02

Chemistry Worksheets With Answers Page 3