10/14/2015 11:45 AM 042.5/10010/12/2015 12:56 PM Gra Print CalculatorPeriodic Ta

Question

10/14/2015 11:45 AM 042.5/10010/12/2015 12:56 PM Gra Print CalculatorPeriodic Table Map d 500.0 mL of 0.150 M NaOH is added to 595 mL of 0.200 M weak acid (K-3.17x10%) What is the pH of the resulting buffer? K. Number pH5324 Explanation Previous > Give Up & View Solution ¢Try Agan Next Ext We can find the pH of the buffer using the Henderson-Hasselbalch equation. pH-pK, + log (HA Also recall that pk, is the negative log of the Ka pK,-- log(k.) about us careerspartners prvacy policy us careers | partners | privacy policy terms of use | contact us | help 12 MacBook Air

Explanation / Answer

Number of moles of HA (weak acid) = 0.595 L x 0.2 M = 0.119 moles

Number of moles of NaOH = 0.500 L x 0.15 M = 0.075 moles

Resulting concentration of [HA] = (0.119 - 0.075) / 1.095 L = 0.0402 M

Resulting concentration of [A-] = (0.075) / 1.095 L = 0.0685 M

pKa = - log Ka = - log (3.17 x 10-5) = 4.499

pH = pKa + log [A-] / [HA] = 4.499 + log 0.0685 / 0.0402 = 4.499 + 0.2315 = 4.2675

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