Question

In: Chemistry

A closed container at 58.1˚C and 285 mm Hg contains a mixture of n-heptane and cyclohexane....

A closed container at 58.1˚C and 285 mm Hg contains a mixture of n-heptane and cyclohexane. Both liquid and vapor phases exist in equilibrium, and the vapor phase contains 32 mol % n-heptane. a) Calculate the mole fractions of the liquid phases. b) Now, the pressure in the container doubles, will the saturation pressure of n-heptane increase, decrease, or stay the same? Justify your answer

Expert Solution

(a) : Given temperature, T = 58.1 C = 58.1 + 273 = 331.1 K

We can calculate the vapor pressure of pure components by applying Antoine equation.

For n-heptane: A = 4.02832, B = 1268.636, C = - 56.199

logP⁰_h = A - B / (C+T) = 4.02832 - 1268.636 / ( - 56.199 + 331.1K)

=> P⁰_h = 0.260 atm = 0.260 atm x ( 760 mm Hg / 1 atm) = 198 mm Hg

For cyclohexane: A = 4.13983, B = 1316.554, C = - 35.581

logP⁰_c = A - B / (C+T) = 4.13983 - 1316.554 / ( - 35.581 + 331.1K)

=> P⁰_c = 0.484 atm = 0.484 atm x ( 760 mm Hg / 1 atm) = 368 mm Hg

From Raoult's law in binary solution,

285 mm Hg = X_h x P⁰_h + (1 - X_h) x P⁰_c

=> 285 mm Hg = X_h x (198 mm Hg) + (1 - X_h) x (368 mmHg) ------- (1)

=> 170 x Xh = 83

=> Xh = 0.488

Hence mole fraction of heptane = 0.488 (answer)

mole fraction of cyclohexane = 0.512 (answer)

(b) If we double the pressure inside the container, the saturation pressure of vapor pressure will also increase as from Raoult's law the pressure inside the container is directly proportional to saturation pressure (vapor pressure)

queen_honey_blossom answered 2 years ago

A mixture of 85% n-heptane, remaining cyclohexane gas at 1 bar and 308 K is compressed...

A mixture of 85% n-heptane, remaining cyclohexane gas at 1 bar and 308 K is compressed to a final state at 1443.47 K and 64.475 bar. Estimate the enthalpy and entropy changes for the process using residual properties and by the Lee/Kessler correlations. In its initial state, the system may be assumed an ideal gas.

A gaseous fuel mixture stored at 744 mm Hg and 298 K contains only methane (CH4)...

A gaseous fuel mixture stored at 744 mm Hg and 298 K contains only methane (CH4) and propane (C3H8). When 13.1 L of this fuel mixture is burned, it produces 858 kJ of heat. What is the mole fraction of methane in the mixture? (Assume that the water produced by the combustion is in the gaseous state.)

A closed system contains an equimolar mixture of n-pentane and isopentane. a) Suppose the system is...

A closed system contains an equimolar mixture of n-pentane and isopentane. a) Suppose the system is initially all liquid at 120°C and a high pressure, and the pressure is gradually reduced at a constant temperature. Estimate the pressures at which the first bubble of vapor forms and at which the last drop of liquid evaporates. Also calculate the liquid and vapor compositions (mole fractions) at those two conditions. b) Now suppose the system starts as a vapor at 1960 mm...

A mixture of n-heptane (A) and ethyl benzene (B) is to be separated in a distillation...

A mixture of n-heptane (A) and ethyl benzene (B) is to be separated in a distillation column operated at 1 atm. The feed flowrate is 300 mol/h and contains 40 mol% n-heptane. 60 % of the feed is liquid. It is required to obtain an overhead product containing 96 mol% n-heptane and a bottom product containing 5 mol% n-heptane. Find the following: a) The distillate and bottom flowrates b) The minimum reflux ratio c) The minimum number of stages d)...

A mixture contains 2.3 mol of cyclohexane (C6H12) and 3.8 mol of 2-methylpentane (C6H14). At 35°C,...

A mixture contains 2.3 mol of cyclohexane (C6H12) and 3.8 mol of 2-methylpentane (C6H14). At 35°C, the vapor pressure of cyclohexane is 150 torr and that of 2-methylpentane is 313 torr. Assume this is an ideal solution. What is the vapor pressure of cyclohexane above the solution?

mixture of 45 mole% n-hexane and 55 mole % n-heptane is subjected to continuous fraction in...

mixture of 45 mole% n-hexane and 55 mole % n-heptane is subjected to continuous fraction in a tray column at 1 atm total pressure. The distillate contains 95% n-hexane and the residue contains 5% n-hexane. The feed is saturated liquid. A reflux ratio of 2.5 is used. The relative volatility of n-hexane in mixture is 2.36. Determine the number of ideal trays required.

1. A mixture of hydrogen and oxygen gases, at a total pressure of 874 mm Hg,...

1. A mixture of hydrogen and oxygen gases, at a total pressure of 874 mm Hg, contains 0.316 grams of hydrogen and 8.78 grams of oxygen. What is the partial pressure of each gas in the mixture? PH2 = mm Hg PO2 = mm Hg 2. A mixture of carbon dioxide and hydrogen gases contains carbon dioxide at a partial pressure of 279 mm Hg and hydrogen at a partial pressure of 477 mm Hg. What is the mole fraction of each...

A mixture of carbon dioxide and nitrogen gases, at a total pressure of 889 mm Hg,...

A mixture of carbon dioxide and nitrogen gases, at a total pressure of 889 mm Hg, contains 7.17 grams of carbon dioxide and 5.38 grams of nitrogen. What is the partial pressure of each gas in the mixture? PCO2 =___(?)___ mm Hg PN2 = __(?)__ mmHg

Consider a mixture of 30% n-butane, 35% n-hexane, 35% n-heptane. If the pressure is 202 kPa,...

Consider a mixture of 30% n-butane, 35% n-hexane, 35% n-heptane. If the pressure is 202 kPa, calculate the bubble point temperature in ?C and the unknown mole fractions. Specify whether the unknown mole fractions are vapor or liquid. .

A mixture of methane (CH4) and ethane (C2H6) is stored in a container at 294 mm...

A mixture of methane (CH4) and ethane (C2H6) is stored in a container at 294 mm Hg. The gases are burned in air to form CO2 and H2O. If the pressure of CO2 is 346 mm Hg measured at the same temperature and volume as the original mixture, calculate the mole fraction of the gases. Mole fraction of methane: _____________ Mole fraction of ethane: _________________