5.Ans :-
(a). The ICE table of phosphoric acid is :
........................................H3PO4 (aq) <--------------------------------> H2PO4- (aq) ................+...................H+ (aq)
Initial ................................0.01 M......................................................0.0 M..............................................0.0 M
Change ......................-0.01α1 .........................................................+0.01α1.........................................+0.01α1
Equilibrium....................0.01(1-α1) M..................................................0.01α1............................................0.01α1
Where α1 = first ionization fraction
At equilibrium, [H+] = 10-pH = 10-5 M (because, pH = - log [H+]
Therefore, 0.01α1 = 10-5
and
α1 = 10-5/0.01
α1 = 10-3
Therefore, first ionization fraction (α1) = 0.001
-------------------------------------
(b).
Now, Equilibrium concentration of H2PO4- = 0.01α1 = 0.01 x 0.001 = 10-5
Therefore,
Required Molar concentration of H2PO4- = 10-5 M
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4. What molar ratio of HPO4 2-to H2PO4-in solution would produce a pH of 7.0? Phosphoric acid (H3PO4), a triprotic acid, has 3 pKa values: 2.14, 6.86, and 12.4. Hint: Only one of the pKa values is relevant here. 5. For a weak acid with a pKaof 6.0, calculate the ratio of conjugate base to acid at a pH of 5.0. 6. Which of these compounds would be the best buffer at pH 5.0: formic acid (pKa 3.8), acetic acid...
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A buffer solution is made by adding 75.52 mL of 1.00 M phosphoric acid (H3PO4, pKa = 2.12) with 10.00 mL of 1.00 M sodium dihydrogen phosphate (NaH2PO4, pKa = 7.21). What is the pH of the buffer solution?
An aqueous solution of 0.100 M phosphoric acid (12.0 mL) is titrated with 0.400 M KOH as shown below. phosphoric acid has three pKas: 2.148, 7.198, 12.375. H3PO4(aq) + OH-(aq) H2PO4-(aq) + H2O(l) H2PO4-(aq) + OH-(aq) HPO42-(aq) + H2O(l) HPO42-(aq) + OH-(aq) PO43-(aq) + H2O(l) Calculate the pH of phosphoric acid solution before any KOH has been added. We were unable to transcribe this imageWe were unable to transcribe this imageWe were unable to transcribe this image
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