Finding out pH of the solution

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Dhamnekar Winod
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Finding out pH of the solution

Post by Dhamnekar Winod »

6.00 g acetic acid and 10.00 g sodium acetate are dissolved in enough water to make 1 L of solution.

a.What is the pH of the solution?
b.If 5 mL of 0.1 M HCl are added to the solution, what is the new pH?
c.If instead 5 mL of 1.0 M KOH are added to the original solution, what is the new pH?

I am working on these questions. 8)
Any science consists of the following process. 1) See 2)Hear 3)Smell,if needed 4)Taste, if needed 5)Think 6)Understand 7)Inference 8)Take decision [Believe or disbelieve, useful or useless, true or false, cause or effect, any other criteria]
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Dhamnekar Winod
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Re: Finding out pH of the solution

Post by Dhamnekar Winod »

Answer to question a.




\(pK_a\) for Ethanoic acid =4.77,\( pH= 4.77 + log(\frac{0.122 M }{0.1 M })=4.85\)
Last edited by Dhamnekar Winod on Sat Apr 10, 2021 3:20 am, edited 3 times in total.
Any science consists of the following process. 1) See 2)Hear 3)Smell,if needed 4)Taste, if needed 5)Think 6)Understand 7)Inference 8)Take decision [Believe or disbelieve, useful or useless, true or false, cause or effect, any other criteria]
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Re: Finding out pH of the solution

Post by ChenBeier »

The chemical reaction is wrong. Its only a mixture of acetic acid and sodium acetate. There is no reaction. You forget the lightning on the right side. Leftside you have a negative charge what gives thunder storm on the right side. :mrgreen:
On the other hand the calculation of pH is correct because you consider the mixture.
Read about buffer solution in your text book or internet. This is relevant for b and c.
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Dhamnekar Winod
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Re: Finding out pH of the solution

Post by Dhamnekar Winod »

Yes. Chemical reaction was wrongly written by me. Thanks for pointing out my mistake. I have corrected the chemical reaction now. is that correct?
Last edited by Dhamnekar Winod on Fri Apr 09, 2021 9:25 pm, edited 1 time in total.
Any science consists of the following process. 1) See 2)Hear 3)Smell,if needed 4)Taste, if needed 5)Think 6)Understand 7)Inference 8)Take decision [Believe or disbelieve, useful or useless, true or false, cause or effect, any other criteria]
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Re: Finding out pH of the solution

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Yes I told you already. But how about b and c?
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Dhamnekar Winod
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Re: Finding out pH of the solution

Post by Dhamnekar Winod »

Answer to question b.

\( pH = 4.77 + log (\frac{0.1215}{0.1005})=4.85\)

Is this answer correct?
Last edited by Dhamnekar Winod on Sat Apr 10, 2021 3:17 am, edited 1 time in total.
Any science consists of the following process. 1) See 2)Hear 3)Smell,if needed 4)Taste, if needed 5)Think 6)Understand 7)Inference 8)Take decision [Believe or disbelieve, useful or useless, true or false, cause or effect, any other criteria]
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Re: Finding out pH of the solution

Post by ChenBeier »

Yes correct
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Dhamnekar Winod
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Re: Finding out pH of the solution

Post by Dhamnekar Winod »

Answer to question c.
Handerson-Hasselbalch equation = pKa + log ([conjugate base]/ [weak acid])

pH =pKa + log ([A⁻][HA]) ,

Hence, pH= 4.74 + log ( 0.127/0.095)= 4.84

Original Concentration of Vinegar - added concentration of 0.005M KOH =0.1 M -0.005 M KOH = 0.095 M

Original concentration of sodium acetate + added concentration of 0.005 KOH = 0.122 M + 0.005 M KOH = 0.127 M
Last edited by Dhamnekar Winod on Sat Apr 10, 2021 4:46 am, edited 3 times in total.
Any science consists of the following process. 1) See 2)Hear 3)Smell,if needed 4)Taste, if needed 5)Think 6)Understand 7)Inference 8)Take decision [Believe or disbelieve, useful or useless, true or false, cause or effect, any other criteria]
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Re: Finding out pH of the solution

Post by ChenBeier »

I dont know where you get the ml. Both acetic acid and sodium acetate are added as the mass. To get ml need specific gravity of 100% Acetic acid and sodium acetate is anyway a salt or need concentration before adding.
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