Final answer:
Calculating the dew temperature for a mixture of water and octane requires equilibrium data which is not provided. The composition of the condensate at dew point is found using the equilibrium data along with the lever rule or activity coefficients if the mixture shows non-ideality.
Step-by-step explanation:
To calculate the dew temperature at 2 bar of a vapor mixture containing 65% water and 35% octane by mole, it is necessary to refer to the vapor-liquid equilibrium data for the water-octane system at the specified pressure. This typically involves using Raoult's Law and Antoine's equation to find the temperatures at which the partial pressures of the components equal the total pressure. However, a direct calculation cannot be provided without the necessary equilibrium data. The composition of the first liquid to condense can be determined by finding the point at which the total vapor pressure equals the system pressure and using the lever rule, assuming ideal behavior or using activity coefficients for non-ideal mixtures.