The line labeled "Raoult's law" represents ideality. For systems that obey this law, the activity coefficients of both A and B are unity over the entire composition range. The equilibrium partial pressures are lower than the pure-component vapor pressures by factors exactly equal to the corresponding mole fraction in the ideal solution:

Such solutions are the exception rather than the rule. For Raoult's law to be followed, the two components must be chemically very similar (e.g., A = benzene and B = toluene - see problem 8.1). However, even metals as similar as nickel and iron exhibit nonideal behavior when alloyed.

In Fig. 8.2, the partial pressure curve joins the Raoult's law line well before xA reaches one. That is, not only is yA ^ 1 as xA ^ 1, but dyA/dxA ^ 0 as well.

Getting Started With Solar

Getting Started With Solar

Do we really want the one thing that gives us its resources unconditionally to suffer even more than it is suffering now? Nature, is a part of our being from the earliest human days. We respect Nature and it gives us its bounty, but in the recent past greedy money hungry corporations have made us all so destructive, so wasteful.

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