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Topic: Acid/Base Equilibrium  (Read 13474 times)

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777888

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Acid/Base Equilibrium
« on: December 07, 2004, 01:15:52 AM »
1)Calculate the % ionization of water (According to H2O<->H+ + OH-) at SATP.

I tried to calculate but I don't know how to calculate the % ionization...

1000g/x=18.02g/1mol
x=55.4939 mol H2O

[H2O]=55.4939mol/L

In pure water,
[H+]=1.0x10-7mol/L
[OH-]=1.0x10-7mol/L

...

2)Is H3PO3 a strong acid? If an acid is monoprotic or diprotic, what does it mean?

I hope someone can teach me! Thank you :)

« Last Edit: December 07, 2004, 01:37:07 AM by 777888 »

Offline AWK

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Re:Acid/Base Equilibrium
« Reply #1 on: December 07, 2004, 01:54:30 AM »
%=100x[H+]/[H2O]
Monoprotic acid split of one proton during dissociation, diprotic - two protons.
H3PO3 is diprotic because it real stucture id (HO)2PHO (one hydrogen atoms forms bond to P not to O) and is a weak acid.
« Last Edit: December 08, 2004, 01:08:21 AM by AWK »
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777888

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Re:Acid/Base Equilibrium
« Reply #2 on: December 07, 2004, 08:56:54 PM »
%=100x[H+]/{H2O]
Monoprotic acid spilt of one proton during dissociation, diprotic - two protons.
H3PO3 is diprotic because it real stucture id (HO)2PHO (one hydrogen atoms forms bond to P not to O) and is a weak acid.
Thank you!

% ionization:
=[H+]/[H2O]100%
=(1.0x10-7)/(55.4939)x100%
=1.8x10-7


But the answer is 10-5%

Is the answer wrong?

777888

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Re:Acid/Base Equilibrium
« Reply #3 on: December 08, 2004, 01:04:19 AM »
3)What are two diagnostic tests that can distinguish a weak acid from a strong acid?

[litmus paper, pH meter, phenolphthalein, are they called diagnostic tests?]

Demotivator

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Re:Acid/Base Equilibrium
« Reply #4 on: December 08, 2004, 01:23:07 PM »
%=100x[H+]/[H2O]  is incorrect if you put in any  value for [H2O] other than 1. For solids and solvents the value in equlibrium equations are always taken as unit activity.
Therefore % = 100x[H+] = 10^-5

777888

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Re:Acid/Base Equilibrium
« Reply #5 on: December 08, 2004, 07:54:14 PM »
%=100x[H+]/[H2O]  is incorrect if you put in any  value for [H2O] other than 1. For solids and solvents the value in equlibrium equations are always taken as unit activity.
Therefore % = 100x[H+] = 10^-5

Thanks
I thought that for every 55.4939 mol of H2O, 1.0x10-7 mol of H+ is produced. Why do you omit H2O?

777888

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Re:Acid/Base Equilibrium
« Reply #6 on: December 08, 2004, 08:44:04 PM »
4.According to the table of acid-base indicators, what is the colour of litmus in a solution with a pH of 8.2, and methyl orange in a solution with a pH of 3.9?
Table of Acid-Base indicators:
Name        Colour of HIn   pH range   Colour of In-
litmus               red           6.0-8.0      blue
methyl orange    red           3.1-4.4     yellow
I don't know how to use the table...what are the meanings of colour of HIn, pH range, and colour of In-? How can I predict the pH of the above problem?

5a)If alizarin yellow is added to a solution, and the colour of the solution turns red, what is the solution pH?
How can I predict the pH? Can someone teach me one? Thank you!
« Last Edit: December 08, 2004, 08:44:51 PM by 777888 »

Offline AWK

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Re:Acid/Base Equilibrium
« Reply #7 on: December 09, 2004, 02:23:09 AM »
Quote
%=100x[H+]/[H2O]  is incorrect if you put in any  value for [H2O] other than 1. For solids and solvents the value in equlibrium equations are always taken as unit activity.
Therefore % = 100x[H+] = 10^-5

Here we are talking about simple stoichiometry, not on equilibrium.
For very diluted solutions concentration and activity are equal.
« Last Edit: December 09, 2004, 02:25:47 AM by AWK »
AWK

777888

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Re:Acid/Base Equilibrium
« Reply #8 on: December 09, 2004, 01:24:12 PM »
3)What are two diagnostic tests that can distinguish a weak acid from a strong acid?

[litmus paper, pH meter, phenolphthalein, are they called diagnostic tests?]
And also, does a strong acid have a lower pH than a weak acid?

777888

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Re:Acid/Base Equilibrium
« Reply #9 on: December 09, 2004, 05:34:42 PM »
Here we are talking about simple stoichiometry, not on equilibrium.
For very diluted solutions concentration and activity are equal.
So is my answer correct???
% ionization:
=[H+]/[H2O]100%
=(1.0x10-7)/(55.4939)x100%
=1.8x10-7%

Thanks~
« Last Edit: December 09, 2004, 05:34:59 PM by 777888 »

777888

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Re:Acid/Base Equilibrium
« Reply #10 on: December 09, 2004, 06:38:03 PM »
4.According to the table of acid-base indicators, what is the colour of litmus in a solution with a pH of 8.2, and methyl orange in a solution with a pH of 3.9?
Table of Acid-Base indicators:
Name        Colour of HIn   pH range   Colour of In-
litmus               red           6.0-8.0      blue
methyl orange    red           3.1-4.4     yellow
I don't know how to use the table...what are the meanings of colour of HIn, pH range, and colour of In-? How can I predict the pH of the above problem?

5a)If alizarin yellow is added to a solution, and the colour of the solution turns red, what is the solution pH?
How can I predict the pH? Can someone teach me one? Thank you!

Anyone knows how to predict the colour? :)

777888

  • Guest
Re:Acid/Base Equilibrium
« Reply #11 on: December 09, 2004, 09:33:43 PM »
4.According to the table of acid-base indicators, what is the colour of litmus in a solution with a pH of 8.2, and methyl orange in a solution with a pH of 3.9?
Table of Acid-Base indicators:
Name        Colour of HIn  pH range  Colour of In-
litmus              red          6.0-8.0      blue
methyl orange    red          3.1-4.4    yellow

......
For question 4, I think that limus in a solution with pH 8.2 is blue. How about methyl orange in a solution with pH 3.9? (not red, not yellow)

......

5a)If alizarin yellow is added to a solution, and the colour of the solution turns red, what is the solution pH?

......

How can I know the pH? There are many possibilities to make the indicator turns red, right?


PLEASE *delete me* I don't understand...
« Last Edit: December 09, 2004, 09:34:54 PM by 777888 »

Offline kevins

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Re:Acid/Base Equilibrium
« Reply #12 on: December 10, 2004, 09:49:56 AM »
1. What is the 'middle' color of the red ~ yellow?

2. What is the pH range of alizarin yellow?  

777888

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Re:Acid/Base Equilibrium
« Reply #13 on: December 10, 2004, 10:54:15 AM »
1. What is the 'middle' color of the red ~ yellow?

2. What is the pH range of alizarin yellow?  

1. Orange I guess...

2. What is the meaning of pH range?

Offline kevins

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Re:Acid/Base Equilibrium
« Reply #14 on: December 10, 2004, 11:05:08 AM »
1. right.

2.I mean the pH range of Colour of HIn and Colour of In-.


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