CHEM 2PC3 Lecture Notes - Lecture 5: Partial Molar Property, Mole Fraction, Vapor Pressure

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27 Sep 2016

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Measures of concentration nj = amount of j (mol) n = total amount of molecules (mol) Binary mixture, on that consists of two species, this general expression becomes. When only a is present, xa = 1 and xb = 0. Partial pressure, pj pj = xjp where xj is the mole fraction of the gas j in the mixture. They can depend on composition xa, xb and interaction. Molar concentration amount of solute in a sample of known volume of solution. Varies with temperatue as the solution expands and contracts. Mole fraction - amount of j molecules expressed as a fraction of the total amount of molecules in the. Xj = nj/n mixture does not vary with temperature. Molality bj = amount of substance divided by the mass of solvent used to prepare the solution. Does not vary with temperature bj = nj/msolvent. Partial molar property contribution (per mole) that a substance makes to an overall property of a mixture.

Related Questions

Ammonia NH3 with Kb = 1.8 x 10^05 is added to 100 mL ofwaterat room temperature and the vapor pressure of water abovethesoultion drops to P = 0.03 atm. What is the pH of the solutioninthe limit that any gas phase NH3 is negliglble.

a) Calculate the vapor pressure above room temperaturewaterwhere delta H vapor = 40.7 kj/mol

I got .815 atm not sure if it's right

b) Calculate the mole fraction of the solvent from Raoult'slawfrom part a.

c) Calculate the total number of moles of the solute fromthesolvent mole fraction.

d) What is the total solute concentration assuming aconstant100 mL volume?

e) Assuming that the concentration determined in thepreviousstep corresponds to the inital amount of added NH3 (aq),what isthe pH of the solution?

1) - A solution was prepared by dissolving 43.0 g of KCl in 225 g of water.

Part A

Calculate the mass percent of KCl in the solution.

Express your answer with the appropriate units.

Part B

Calculate the mole fraction of the ionic species KCl in the solution.

Express the concentration numerically as a mole fraction in decimal form.

X =

Part C

Calculate the molarity of KCl in the solution if the total volume of the solution is 239 mL.

Express your answer with the appropriate units.

Part D

Calculate the molality of KCl in the solution.

Express your answer with the appropriate units.

2)- How much energy is required to heat 90.7 g acetone (molar mass=58.08 g/mol) from a solid at -154.0Â°C to a liquid at -42.0Â°C? The following physical data may be useful.

ÎH_fus = 7.27 kJ/mol
C_liq = 2.16 J/gÂ°C
C_gas = 1.29 J/gÂ°C
C_sol = 1.65 J/gÂ°C
T_melting = -95.0Â°C

3)- The decomposition of XY is second order in XY and has a rate constant of 7.12Ã10^â3 Mâ1â sâ1 at a certain temperature.

Part A

How long will it take for the concentration of XY to decrease to 12.5% of its initial concentration when the initial concentration is 0.200 M?

Part B

If the initial concentration of XY is 0.050 M, what is the concentration of XY after 600 s ?

4) - This table displays the vapor pressure of a substance at several different temperatures.

Part A

Use the data to determine the heat of vaporization of the substance in units of kJ/mol. Hint: use Excel

CHEM 2PC3 Lecture Notes - Lecture 5: Partial Molar Property, Mole Fraction, Vapor Pressure

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