Ask Experts Questions for FREE Help !
Ask
    sumernavale's Avatar
    sumernavale Posts: 1, Reputation: 1
    New Member
     
    #1

    Apr 15, 2009, 12:14 AM
    Find out association?
    2 gm C6H5COOH dissolved in 25 gm of benzene shows a depression in freezing point equal to 1.62 k.Molar depression constant for benzene is 4.9 k kg \mol.What I sthe percentage association of acid if it forms double molecules(dimmer) solution?
    Perito's Avatar
    Perito Posts: 3,139, Reputation: 150
    Ultra Member
     
    #2

    Apr 15, 2009, 05:06 AM

    Freezing point depression is discussed here along with some cryoscopic constants including the constant for benzene (they give a value of 5.12).

    Freezing-point depression - Wikipedia, the free encyclopedia

    The freezing point depression is given as ΔTf = Kf · mB (Equation 1) where ΔTf is the change in freezing point, Kf is the cryoscopic constant and m is the molality of the solution. C is the molality of the solution.

    The molality of the solution, mB, is often calculated from this equation:

    mB = msolute · i. (Equation 2)

    where msolute is the molality of the solute and "i" is the number of ions or particles formed in solution. It's not an exact science.

    In your case, the freezing point depression is 1.62 Kelvins. You are also given the freezing point molar (not molal for some reason) depression constant (4.9 Kelvin Kilograms / mol).

    In this case, you're given 2 grams of benzoic acid. The molecular weight of benzoic acid is 122.12 g/mol. That would give you

    of benzoic acid.

    However, you are told that benzoic acid forms a dimer in solution. Thus, you have only half that number of moles

    of benzoic acid dimer -- IF IT WERE 100% associated (which it's not).

    The problem requires that you figure out mB and then figure out "i" from equation 2 (you assume molarities instead of molalities) since your cryoscopic constant is "per mole" instead of "per molal". You'll get a number between 0.0164 moles and 0.00819 moles. You must assume that "i" is linearly dependent on the association.

    Give it a try and if you're still having trouble, post your work.

Not your question? Ask your question View similar questions

 

Question Tools Search this Question
Search this Question:

Advanced Search


Check out some similar questions!

Word association [ 2 Answers ]

Minute is to hour as second is to? Ice is to water as rock is to? Better is to worst as slower is to ?

Association Lien [ 1 Answers ]

My association put a lien on my house. Do they have to notifity me? How am I suppose to know what their next course of action is or does it just sit their unil it is satisfied? How can a court issue a lien without knowing both side to verify it the amount is correct or it the debt is even owed?

Homeowners association fee [ 2 Answers ]

We bought a house in this subdivision that was going up. We were verbally told by the seller that a home owenrs association would be in place once all the homes were built and that the first year association fee would be mandatory but after that it was optional to be part or not of this...

Condo association [ 1 Answers ]

Our assessment fees are already high,owners have a hard time paying,so we need help. One of the owners has a lien on their property, because of unpaid assement fees. This owners owes us almost 5.000 Where can I ask for help for our condominium association ? We need money to pay our bills and ...

Association vs. Landlord [ 5 Answers ]

I am currently trying to rent out my 2 bedroom /2 bath condo to this 2 guys that is currently renting a place within the same building. They expressed interest in renting my place and gave me a deposit. Unfortunately, when I approached the association about this decision, they told me that they...


View more questions Search