A buffer solution is made that is 0.449 M in HNO_2 and 0.449 M in KNO_2. (1) If
ID: 513046 • Letter: A
Question
A buffer solution is made that is 0.449 M in HNO_2 and 0.449 M in KNO_2. (1) If K_a for HNO_2 is 4.50 times 10^-4, what is the pH of the buffer solution? (2) Write the net ionic equation for the reaction that occurs when 0.126 mol KOH is added to 1.00 L of the buffer solution. A buffer solution is made that is 0.369 M in HCN and 0.369 M in KCN. (1) If Ka for HCN is 4.00 times 10^-10, what is the pH of the buffer solution? (2) Write the net ionic equation for the reaction that occurs when 0.090 mol HI is added to 1.00 L of the buffer solution. Use H_3 O^+ instead of H^+.Explanation / Answer
1) The equation for the dissociation of weak acid HNO2 is given as
HNO2(aq) + H2O (l)-------> NO2- + H3O+(aq)
Henderson-Hasselbalch equation for pH is
pH = pKa + log {[conjugate base]/[acid]}
pH = pKa + log{[NO2-]/[HNO2]
pKa = -logKa
pKa = -log(4.50 * 10-4)
pKa = 3.35
pH = 3.35 + log { 0.449/0.449}
pH = 3.35
2) Net ionic equation is
HNO2 + KOH -----> KNO2 + H2O
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