Question

Calculate the vapor pressure of water above the solution. The vapor pressure of pure water at this temperature is 0.0313 atm. Assume complete dissociation.

Answer 1

The vapor pressure of water is used to calculate the density of water vapor at 40.0°C using the ideal gas law, where the final density should match the known saturation vapor density of 51.1 g/m³.

Step-by-step explanation:

To calculate the density of water vapor using the vapor pressure and the ideal gas law, we use the expression PV = nRT, where P is the pressure, V is the volume, n is the number of moles, R is the gas constant, and T is the temperature in Kelvin. With the vapor pressure given as 7.34 × 10³ N/m² (which is equivalent to Pascals) and the temperature at 40.0°C, or 313.15 K, we can calculate the number of moles of water vapor. From there, using the molar mass of water (18.01528 g/mol), we can solve for the density in g/m³.

The steps are as follows:

• Convert the vapor pressure to moles using the gas constant for R (8.314 J/mol·K).
• Calculate the moles of water vapor per cubic meter using the ideal gas equation.
• Multiply the moles by the molar mass of water to find the density.
• After calculation, the density of water vapor should be close to 51.1 g/m³, which is the saturation vapor density at that temperature.

Answer 2

This question is incomplete, the complete question is;

The density of a 0.438 M solution of potassium chromate (K2CrO4) at 298 K is 1.063 g/mL.

Calculate the vapor pressure of water above the solution. The vapor pressure of pure water at this temperature is 0.0313 atm. Assume complete dissociation.

Pvap = ________atm

Answer:

Pvap = 0.0306 atm

Step-by-step explanation:

we know that; 1 L = 1000 mL of the solution

Mass of solution = volume x density

= 1000 x 1.063 = 1063 g

Moles of K2CrO4 = volume x concentration

= 1 x 0.438 = 0.438 mol

Mass of K2CrO4 = moles x molar mass = 0.438 x 194.19 = 85.055 g

Mass of water = 1063 - 85.055 = 977.945 g

Moles of water = mass / molar mass

977.945 / 18.02 = 54.27 mol

K2CrO4 => 2 K+ + Cr2O42-

Moles of ions = 3 x moles of K2CrO4

= 3 x 0.438 = 1.314 mol

Vapor pressure of solution = mole fraction of water x vapor pressure of water

= (54.27 / (54.27 + 1.314)) x 0.0313

= 0.0306 atm