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# What are the molarity,molality, and mole fraction of the solution

Submitted by jp on Sun, 07/05/2009 - 18:39

If you could please show me how to solve the following problems step by step that would be wonderful
thanks

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?

Hint for Question 4 -  Look up Graham's Law.

Show us some work and we'll try to help you figure out the rest.

spock wrote:

Hint for Question 4 -  Look up Graham's Law.

Show us some work and we'll try to help you figure out the rest.

Okay so number 4 I thought since o2 is 32 if it is .5times as fast you would do 32 times 2 which equals 64 giving us the MW?
Grahams law is rate A/Rate B = square root of mol B/Mol A. I dont know how to apply the formula to this problem though

Graham's Law tells us that the rates of diffusion are inversely related to the square root of the molecular masses.  Your argument is incorrect because you are assuming that the molecular masses are inversely related to the molecular masses.

From the problem:   rate of unknown / rate of O2 = .5

Using Graham's Law:  rate unknown/Rate O2 = square root of (mole mass O2/Mole mass unknown)

Subsitute the value from the first equation into the second equation:
.5 =  square root of (mole mass O2/Mole mass unknown)
Square both sides to get rid of the sqr root:
.25 =   32 / Mol unknown
Rearrange and solve for mole mass of the unknown:
mole mass of unknown = 32/.25

yay thats funny I actually firgured that out before I saw your post. It feels to finally get it. Since you said Grahmans Law I tired using it anyway possible and got it. :)

So, I ahve 2 questions I know it says ask one question question at a time but my test is tonight and I wanna understand the concepts before I take it.

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?

So if this problem I used PV=nRT
I first found the moles(n) by doing (.98atm)(.0276L)/(.082)(296K)
So n=.001
then I found
a. bye P= .001(.082)(296K)/.00276 L and got .88 atm
b. I did V=.001(.082)(296K)/.88atm =.03
c. I said it was n=.001
is this right? if not can you please show me the right way to do it

the other question I have is
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
I said steam is 50g(x)(125C)
ice is 50(X)(-125C)
and then I set them equal to each other
I got x=1
Is this the right apporach if not can you please show me the right way.