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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: dagr8est on April 09, 2006, 02:19:19 PM

Title: Another Ksp Related Question
Post by: dagr8est on April 09, 2006, 02:19:19 PM

Sigh, I am starting to think that every answer on this answer key is wrong...  If someone can confirm that I did this question correctly, I will just disregard the answer key for the rest of the questions.

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Calculate the Ag⁺ concentration required to start a precipitation of AgBrO₃ from a solution containing 0.50g of NaBrO₃ per 0.300 litre.  Ksp of AgBrO₃ = 5.3(10^-5)

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[BrO₃^-] = [NaBrO₃] = 0.50g(1mol/127.9g)(1/0.300L) = 0.013M

Ksp = [Ag⁺][BrO₃^-]
5.3(10^-5) = [Ag⁺](0.013M)
4.1(10^-3)M = [Ag⁺]

Answer key says it's 4.5(10^-11)M...

Title: Re: Another Ksp Related Question
Post by: Borek on April 09, 2006, 02:52:45 PM

Seems to me it should be 4.8*10^-3, so both answers are wrong. Check molar mass of sodium bromate.

Title: Re: Another Ksp Related Question
Post by: dagr8est on April 09, 2006, 03:15:42 PM

Oh yeah whoops, I forgot to include sodium.  I agree it should be 4.8(10^-3)M then.  I guess this answer key is just completely wrong then.  Thanks for the help on both questions. ;D

Title: Re: Another Ksp Related Question
Post by: AWK on April 10, 2006, 12:15:47 AM

MM  of NaBrO3 is ~ 151