easy chem problem but confused

[IWantH2O]

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wat is the boiling point temperature of a 0.5 m solution of Na2SO4 dissolved in water at 1 atm? (kb=.512 C/m)

 

[xhamburgersamx]

(0.5) x (0.512) x 3 (dissociation of Na"2"So4) add the answer to 100

 

[artanis]

wat is the boiling point temperature of a 0.5 m solution of Na2SO4 dissolved in water at 1 atm? (kb=.512 C/m)

Hey this is referring to colligative properties, more specifically boiling point elevation. The formula of concern is as follows:

deltaT = m*Kb*i
Tnew-Toriginal = m*Kb*i

Toriginal is the original boiling point of water (100 degrees celsius), m is molality in moles/kg, Kb is the constant given, and i is the number of dissociated ions in solution

So in this example, Na2SO4 --> 2Na + SO4, so therefore i = 3.

Then just plug, you'll get Tnew = Toriginal + (0.5)(0.512)(3)
Then theres your new boiling point. Be careful, they may not ask you the boiling point, but just the "elevation" at which point you just calculate Tnew-Toriginal.

Hope this helps.

 

[IWantH2O]

Hey this is referring to colligative properties, more specifically boiling point elevation. The formula of concern is as follows:

deltaT = m*Kb*i
Tnew-Toriginal = m*Kb*i

Toriginal is the original boiling point of water (100 degrees celsius), m is molality in moles/kg, Kb is the constant given, and i is the number of dissociated ions in solution

So in this example, Na2SO4 --> 2Na + SO4, so therefore i = 3.

Then just plug, you'll get Tnew = Toriginal + (0.5)(0.512)(3)
Then theres your new boiling point. Be careful, they may not ask you the boiling point, but just the "elevation" at which point you just calculate Tnew-Toriginal.

Hope this helps.

ya thats wat i did but kaplan solved it without multiplying by 3..they jus multiplied 0.5 by 0.512 and got 0.256...added that to 100 and gave the answer


is that a typo cuz im pretty sure u got to multiply by 3

 

[IWantH2O]

anybody.................should i jus assume its a typo or am i missing something

 

[Electrons]

ya thats wat i did but kaplan solved it without multiplying by 3..they jus multiplied 0.5 by 0.512 and got 0.256...added that to 100 and gave the answer


is that a typo cuz im pretty sure u got to multiply by 3

I would have done the same way but what explanation did it give? Type it up, maybe we can figure it out for you...