A buffer solution is made that is 0.370 M in CH 3 COOH and 0.370 M in CH 3 COO .
ID: 1004227 • Letter: A
Question
A buffer solution is made that is 0.370 M in CH3COOH and 0.370 M in CH3COO .
(1) If Ka for CH3COOH is 1.80×10-5, what is the pH of the buffer solution?
(2) Write the net ionic equation for the reaction that occurs when 0.080 mol HI is added to 1.00 L of the buffer solution.
Use H3O+instead of H+.
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A buffer solution is made that is 0.416 M in H2S and 0.416 M in NaHS.
(1) If Ka for H2S is 1.00×10-7, what is the pH of the buffer solution?
(2) Write the net ionic equation for the reaction that occurs when 0.111 mol HI is added to 1.00 L of the buffer solution.
Use H3O+ instead of H+.
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A buffer solution is made that is 0.339 M in H3PO4 and 0.339 M in NaH2PO4.
(1) If Ka for H3PO4 is 7.50×10-3, what is the pH of the buffer solution?
(2) Write the net ionic equation for the reaction that occurs when 0.074 mol NaOH is added to 1.00 L of the buffer solution.
Explanation / Answer
1) pH of acidic buffer = pka + log(salt/acid)
pka = -logka = -log(1.8*10^-5)= 4.74
pH = 4.74+log(0.37/0.37) = 4.74
2) H3O^+ + CH3COO^- ---> CH3COOH + H2O
1) pka = -logka = -log(1.0*10^-7)= 7
pH = 7+log(0.416/0.416) = 7
2) H3O^+ + HS^- ---> H2S + H2O
1) PKa = -logka
= -log(7.5*10^-3) = 2.125
2) OH^- + H3PO4 ----> H2PO4^- + H2O
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