Some Simple Applications of Raoults and Henrys Laws

In Examples 3.1 and 3.2 the calculation was simple, because we knew from Table 3.1 that the liquid was practically pure water and that the concentration of water vapor in air was small. In general, for solutions involving more than two species we will not know this, and will have as many species equilibrium equations to solve simultaneously as there are species present, normally by trial and error. Before the age of computers this calculation was a giant pain, but our computers now do it for us quickly and easily. The three equilibrium equations from Examples 3.1 and 3.2 are 

Example 3.3 Repeat the calculation of Table 3.1, using the above six equations, and not making the simplifications previously used. 

Solving this set of six linear equations in six unknowns by any of the standard simultaneous linear equation methods, we find the values shown in Table 3.A.  

6 SOME SIMPLE APPLICATIONS OF RAOULT S AND HENRY S LAWS 

If we know the system temperature we can use Raouh s law (and the assumption that the vapor is an ideal gas) to solve some simple vapor-liquid equilibrium problems. 

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