Determine the amounts and mole fractions for the phases that are formed. In a container, 28 moles of B and 12 moles of A are mixed. Where f L and f V are the mole fractions (or percentages, depending on the graph ) of the liquid and vapor phases, respectively.Р’В Note that obviously f L and f V have no units Р’В while n L and n V do have units (moles, grams, etc.). Р”В¬onsider the same system as above, having another form of the lever rule below: Equations for calculating the liquid and vapor fractions using the lever arms.Р’В Source: Gabriel BolР“Вvar. The previous expression for the lever rule is used to calculate the quantities (masses, moles, etc.) of the phases in equilibrium at once.Р’В However, the best known version of the lever rule we can calculate the fractions or percentages of each phase, taking only the distances between X B, X B L and X B V. Thus, the lever rule will allow us to calculate the total moles n L and n V provided that the total moles of the mixture are known, n T ( n T = n L + n V ). This equation is very similar to the one that describes the balance of the masses on a seesaw with a fulcrum: These last two mathematical expressions are the lever rule.Р’В Note that X B РІР‚вЂњ X B L is the distance between points C and D Р’В and X B V РІР‚вЂњ X B, is the distance between the points DE: the two halves of the joint line (lever arms). N L (X B РІР‚вЂњ X B L ) = n V (X B V РІР‚вЂњ X B ) (3) The lever rule can be applied directly, taking into account the values РІР‚вЂ№РІР‚вЂ№plotted on the abscissa axis, where generally the global fractions or percentages of the most volatile component go, in the case of liquids Р’В or refractory, in the case of metals in their alloys. The physical and mathematical principle of the lever is also used for chemical purposes and in the physics of materials.Р’В Source: Jimbowley, CC BY-SA 3.0, via Wikimedia Commons This rule applies to phase diagrams for binary systems, regardless of the type of system itself.Р’В That is to say, the phases can be solid, as happens with alloys Р’В or liquid and gaseous, as we see in systems in liquid-vapor equilibrium. The lever rule is a mathematical procedure that allows us to calculate the fractions, percentages or quantities of the phases present in equilibrium within a binary system.Р’В It is not only mathematical, but also quite graphic and assertive, being very useful in physicochemical and engineering calculations.

Inverse lever arm rule ternary diagram