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  1. #1 help with assignment 
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    please help

    (A)
    An aqueous solution of NH4Cl has a molal concentration of 1.193 molkg^-1. Its density is 1.0170 gmL^-1.


    1) Calculate the molar concentration of NH4Cl.

    ----- mol/L

    2)Calculate the mass percent of NH4Cl in the solution.

    -----%

    3)What is the mole fraction of NH4Cl in the solution?

    -----


    (B)
    What mass (g) of AlCl3 would have to be dissolved in 150 mL of water to give a solution that has a vapour pressure of 4.6310^3 Pa at 35C? Assume complete dissociation of the solute and ideal solution behavior. At 35C, the vapour pressure of pure water is 5.6310^3 Pa.


    -----

    (C)
    What is the approximate osmotic pressure of a 0.1192 molkg^-1 solution of LiCl at 10 C? The freezing point of this solution is -0.415 C. Express your answer in Pa.
    -----


    (D)
    The vapour pressure of a mixture of 150 g of acetone and 41.6 g of an unknown compound is 0.86610^4 Pa at 20 C. The vapour pressure of pure acetone at 20 C is 0.73710^4 Pa, while that of the pure unknown is 1.4010^4 Pa. What is the approximate molar mass of the unknown?

    -----gmol^-1


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  3. #2  
    Moderator Moderator AlexP's Avatar
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    See what you can do, post it, and then someone can help you from there.


    "There is a kind of lazy pleasure in useless and out-of-the-way erudition." -Jorge Luis Borges
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  4. #3  
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    what?
    help pls
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  5. #4  
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    mohab, in order for us to help you, we have to see that you've done some work first. It's not our job to remove thought from the equation that is your homework, so once you've posted the thoughts that you've had on this, we may be able to help you, but you first have to show that you've attempted the problem. Sorry, no free answers
    Wise men speak because they have something to say; Fools, because they have to say something.
    -Plato

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  6. #5  
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    I understand that, and i apreciate ur reply..
    i passed chemistry 1 with my course work and some pushes from the book..
    i dont know how i am going to pass chemistry 2.. because i really suck at chemistry.. this assignment has 10% for me, and i dont really know where to get help ..

    but i tried solving many times, even had a few friends over to help me but we couldnt figure it out ..

    i understand the laws for molar fraction and mass percent ..etc like the equations..
    i tried over and over but everytime i tried i would get a different answers, and all the 10^3 or -1 or 6 or w.e just scares me more

    thx again for replying
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  7. #6  
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    a1) if you know the density, can you tell me how many kg in a liter? Once you find , if you know how many , can you find the ?
    Wise men speak because they have something to say; Fools, because they have to say something.
    -Plato

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  8. #7  
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    Quote Originally Posted by Arcane_Mathematician
    a1) if you know the density, can you tell me how many kg in a liter? Once you find , if you know how many , can you find the ?
    am really sorry. i didnt understand a word, that was like another language to me..
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  9. #8  
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    Are you a high school student or are you in a college course? If you don't understand units, I'm not really sure how to simplify things further for you to understand.
    Wise men speak because they have something to say; Fools, because they have to say something.
    -Plato

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  10. #9  
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    college course
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  11. #10  
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    my advice is to drop chem 2 and take an intro physics class, so you can learn how to apply units.
    Wise men speak because they have something to say; Fools, because they have to say something.
    -Plato

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