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Topic: Help on Ka and pH problem  (Read 5642 times)

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Offline rmszymanski726

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Help on Ka and pH problem
« on: March 09, 2014, 10:58:13 AM »
I am attempting to solve this probelm but after trying several different methods (ICE table) I can't figure it out:
Sodium benzoate (C6H5CO2Na) is used as a food preservative.
a. Calculate the pH in 0.056M sodium benzoate; Ka for benzoic acid (C6H5CO2H) is 6.5×10−5.
b. Calculate the concentrations of all species present (Na+, C6H5CO−2, C6H5CO2H, H3O+ and OH−) in 0.056M sodium benzoate.

Offline Borek

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Re: Help on Ka and pH problem
« Reply #1 on: March 09, 2014, 01:37:31 PM »
Let's start with a. Show what you did.
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Offline DanChen2014

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Re: Help on Ka and pH problem
« Reply #2 on: March 12, 2014, 02:02:11 AM »
C6H5CO2- + H2O =====C6H5CO2H + H3O+

Kb=Kw/Ka

Offline Borek

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Re: Help on Ka and pH problem
« Reply #3 on: March 12, 2014, 03:31:57 AM »
C6H5CO2- + H2O =====C6H5CO2H + H3O+

Think it over.
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Offline DanChen2014

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Re: Help on Ka and pH problem
« Reply #4 on: March 12, 2014, 09:36:49 AM »
C6H5CO2- + H2O =====C6H5CO2H + H3O+

Kb=Kw/Ka
CORRECTION:
C6H5CO2- + H2O =====C6H5CO2H + OH-

YOU will have pOH.

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