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# What are the molarity,molality, and mole fraction of the solution? and other non-related questions

Submitted by jp on Sun, 07/05/2009 - 18:42

1.      An aqueous solution of ethylene glycol(C2H6O2) is 40% ethylene glycol by mass, and has a density of 1.05 g/ml. What are the molarity,molality, and mole fraction of the solution?

2.      How many pounds of carbon dioxide are produced from burning one gallon of gasoline? Assume gasoline is 100% octane, and the density of octane is .78 g/ml. Show the balanced reaction.

3.      How many grams of propane are in a 35L container at 40 degrees C and 900 torr?

4.      A gas diffuses only .5 times as fast as an oxygen molecule at the same temperature. What is the molecular weight of the gas?

5.      The vapor pressure of pure water at 20 degrees C is 17.5 torr. What is the vapor pressure at 20 degreesC above a solution that has 85.5 g of sucrose and 75 g of urea dissolved per kg of water?

6.      A gas occupies 10 liters at standeredconditions. What volume will it occupy at 20 degrees C and 700 torr

7.      Calculate the amount of heat in kilograms when 50 grams of steam at 125 degrees C are converted to 50 grams of ice at -125 degrees C

8.      46 L of he and 12 L of oxygen both at 25 C and 760 torr were put in a tank with a volume of 5L. Calculate partial pressure of each gas and total pressure in the tank at 25C

9.A 27.6 ml volume of chlorine gas is collected over water at 23 degrees Celsius and 750 torr. The mass of the gas is 78.4 mg. The vapor pressure of water is 21 torr.
a.  What is the pressure of the chlorine gas?
b.  What volume does the chlorine gas occupy?
c.  How many moles of chlorine gas are collected?

The rules of this site ask you to post only one question at a time.  It also asks that you make an attempt to solve the problems, and we'll then correct any mistakes and make sure that you are pointed in the right direction.

Your two posts make it appear that you would like us to do your homework for you!

However, I will give you a couple of pointers.

Several of your questions will require the ideal gas equation to reach a solution.  For instance

3.      How many grams of propane are in a 35L container at 40 degrees C and 900 torr?
In this case you need to solve the ideal gas equation (PV=nRT) for the number of moles:
n= PV / RT  where P is the pressure (900 Torr = 1.18 atm) in atmospheres, V is volume in Liters, T is the temperature in Kelvin (oC + 273), and R is the Universal gas constant (R= .082 Liter atm/mol K).  Plug those values in and solve for n (the number of moles.

To find the mass of propane you will need to multiply the number of moles of propane (n) by the molar mass of propane (which can be calculated from the molecular formula of Propane (C3H8) and the atomic masses of C and H found in the Periodic Table.

Problem 6 can also be solved using the ideal gas equation.  In that case, you will find the number of moles (n) of oxygen gas at STP by dividing the volume of the oxygen by the molar volume of a gas at STP (22.4 L/mol).  Once you know the value of n then you can solve the ideal gas equation for V:

V = n R T / P

Plug in your values for n, T, and P and find the Volume (make sure that your units agree!  T in Kelvin, P in atmospheres).

thanks,
I was wondering how I would even start this problem
5.      The vapor pressure of pure water at 20 degrees C is 17.5 torr. What is the vapor pressure at 20 degreesC above a solution that has 85.5 g of sucrose and 75 g of urea dissolved per kg of water?

Try looking up Raoult's Law.  It is an equation that describes the relationship between mole fractions and vapor pressure.

spock wrote:

Try looking up Raoult's Law.  It is an equation that describes the relationship between mole fractions and vapor pressure.

I foudn Raoults Law:
Pof a= P degree of A times X of A but I still dont understand how to use this formula or where to plug what in if you could please lead me in the right direction

P of A is the vapor pressure of substance A above a solution containing a substance A  (In your case A is water and this is what you are looking for).

P of Ao is the vapor pressure of substance A when it is pure (you are given the vapor pressure of pure water in the problem)

X of A is the mole fraction.  The mole fraction can be calculated by calculating the number of moles of each substance.  In your case you will need to calculate the number of mole (n) for 3 substances: water, glucose, and urea.

n for water = mass of water / mole mass of water

n for sucose = mass of glucose / mole mass of sucose    (sucrose = C12H22O11)
n for urea  = mass of urea / mole mass of urea            (urea= N2H4CO)

Once you've found the moles of each substance you can find the mole fraction by dividing the moles of water by the total number of moles.  The equation for this in your case is:
X of water =  moles of water / (moles of water + moles of sucrose + moles of urea)

Once you done this you will have both the mole fraction of the water and the vapor pressure of pure water so you can plug into the equation for Raoult's Law and find your answer.