# Chemical and phase equilibria, A12 and A21 for Infinitely dilute.

• enymh2
In summary, the activity coefficients at infinite dilution for isopropanol and water at 80°C and 1 atm are 11.825 and 2.986 respectively. The van Laar Coefficients A12 and A21 can be calculated using the equation A12=lnγ (1+((x2lnγ2)/( x1lnγ1))^2) and the Antoine equation for the two liquids. When calculating A12, the value of x1 becomes 0 and when calculating A21, the value of x2 becomes 0. Simply using A12=lnγ may not give the correct answer.
enymh2

## Homework Statement

(a) The activity coefficients at infinite dilution for isopropanol and water are 11.825 and 2.986 respectively at 80°C and 1 atm.
i) Calculate the van Laar Coefficients A12 and A21 2. Relevant equation.
A12=lnγ (1+((x2lnγ2)/( x1lnγ1))^2)
The eqaution for A21 is the same except 1 and 2 are reversed.

Given the antoine eqaution for the two liquids also.

## The Attempt at a Solution

At infinitely dilute solution, for A12 the x1 value will become 0 and for A21 the x2 value will become 0. Therefore i would be left with just A12=lnγ? but this doesn't give me the right answer.

I've also tried substituting the values of γ but this doesn't seem to work either. Any help would be appreciated!

## 1. What is chemical equilibrium?

Chemical equilibrium is a state in which the forward and reverse reactions of a chemical reaction occur at equal rates. This means that the concentrations of all reactants and products remain constant over time.

## 2. What is phase equilibrium?

Phase equilibrium is a state in which two or more phases of a substance coexist without any net change in the overall composition of the system. This occurs when the rate of phase change in one direction is equal to the rate of phase change in the opposite direction.

## 3. What is the A12 parameter for infinitely dilute solutions?

The A12 parameter is a measure of the thermodynamic tendency of a substance to mix with another substance in an infinitely dilute solution. It is also known as the activity coefficient, and it describes the non-ideal behavior of solutions at low concentrations.

## 4. What is the A21 parameter for infinitely dilute solutions?

The A21 parameter is similar to the A12 parameter, but it measures the thermodynamic tendency of a substance to mix with another substance in an infinitely dilute solution in the opposite direction. It is also known as the inverse activity coefficient.

## 5. How are the A12 and A21 parameters used in chemical and phase equilibria calculations?

The A12 and A21 parameters are used to calculate the activity coefficients of substances in solutions at low concentrations. These coefficients are then used in equilibrium calculations to determine the concentrations of reactants and products in a system at equilibrium.

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