Use the diagram provide to answer the question
a). Which of the two liquids is volatile
It is not possible to determine which of the two liquids is volatile from the diagram provided.
Which of the two liquids is volatile.Hexane or heptane in pressure/temperature composition diagrams.
Hexane is more volatile than heptane based on pressure/temperature composition diagrams. This is because hexane has a lower boiling point and lower molecular weight compared to heptane, making it easier for its molecules to escape into the air as vapor.
For a solution containing 1mole each of hexane and heptane, estimate the vapour pressure in torr at 70°C when vaporization on reduction of external pressure just begins.
To estimate the vapor pressure of the solution at 70°C, we need to calculate the Raoult's law vapor pressure of each component and then determine the total vapor pressure of the solution.
According to Raoult's law, the vapor pressure of a component in a solution is given by:
P = Po*X
where P is the vapor pressure of the component in the solution, Po is the vapor pressure of the pure component, and X is the mole fraction of the component in the solution.
At 70°C, the vapor pressures of hexane and heptane are as follows:
Po_hexane = 249 torr
Po_heptane = 105 torr
To determine the mole fraction of each component in the solution, we need to know the total moles in the solution. Since we have 1 mole of hexane and 1 mole of heptane, the total moles in the solution are 2.
The mole fraction of hexane can be calculated as follows:
X_hexane = number of moles of hexane / total number of moles in the solution
= 1 / 2
= 0.5
Similarly, the mole fraction of heptane can be calculated as follows:
X_heptane = number of moles of heptane / total number of moles in the solution
= 1 / 2
= 0.5
Now, we can use Raoult's law to calculate the vapor pressure of each component in the solution:
P_hexane = Po_hexane * X_hexane
= 249 torr * 0.5
= 124.5 torr
P_heptane = Po_heptane * X_heptane
= 105 torr * 0.5
= 52.5 torr
The total vapor pressure of the solution is the sum of the vapor pressures of each component:
P_total = P_hexane + P_heptane
= 124.5 torr + 52.5 torr
= 177 torr
Therefore, the vapor pressure of the solution at 70°C when vaporization on the reduction of external pressure just begins is approximately 177 torr.
What is the vapour pressure of the solution at 70 degrees celsius when just one drop of the liquid remains
When just one drop of the liquid remains, the solution is said to be at its dew point. At this point, the vapor pressure of the solution is equal to the saturated vapor pressure of the solution at that temperature.
To find the saturated vapor pressure of the solution at 70°C, we need to find the mole fraction of each component in the vapor above the solution using Raoult's law.
For hexane,
P_hexane = Po_hexane * X_hexane
= 249 torr * 0.5
= 124.5 torr
For heptane,
P_heptane = Po_heptane * X_heptane
= 105 torr * 0.5
= 52.5 torr
The mole fraction of hexane and heptane in the vapor can be calculated using Dalton's law:
P_total = P_hexane + P_heptane
X_hexane_vapor = P_hexane / P_total
= 124.5 torr / (124.5 torr + 52.5 torr)
= 0.703
X_heptane_vapor = P_heptane / P_total
= 52.5 torr / (124.5 torr + 52.5 torr)
= 0.297
Now, we can use the Antoine equation to find the saturation pressure of the solution at 70°C:
log(P) = A - (B / (T + C))
where P is the saturation pressure in torr, T is the temperature in °C, and A, B, and C are constants for each component. For hexane, the constants are:
A = 6.89272
B = 1172.32
C = 227.00
For heptane, the constants are:
A = 6.92764
B = 1251.17
C = 235.45
For a solution of hexane (X_hexane_vapor = 0.703) and heptane (X_heptane_vapor = 0.297), the saturation pressure can be calculated as follows:
log(P) = X_hexane_vapor * (A - (B / (T + C))) + X_heptane_vapor * (A - (B / (T + C)))
log(P) = 0.703 * (6.89272 - (1172.32 / (70 + 227))) + 0.297 * (6.92764 - (1251.17 / (70 + 235)))
log(P) = 3.728
P = 10^3.728
P ≈ 4214 torr
Therefore, the vapor pressure of the solution at 70°C when just one drop of the liquid remains is approximately 4214 torr.