How would you use the Henderson-Hasselbalch equation to calculate the pH of a buffer solution that is 0.27 M in formic acid (HCO2H) and 0.50 M in sodium formate (HCO2Na)?
Your buffer solution contains formic acid,
The Henderson - Hasselbalch equation allows you to calculate the pH of the buffer by using the
#color(blue)("pH" = pK_a + log( (["conjugate base"])/(["weak acid"])))#
Before plugging in the values given to you, try to predict what you expect the pH of the solution to be. Notice that at equal concentrations of weak acid and conjugate base, the log term is equal to zero.
In this case, the pH of the solution will be equal to the acid's
This means that the pH will actually increase, which is what you should expect to see in this case.
#"pH" = pK_a + log( (["HCOO"^(-)])/(["HCOOH"]))#
#"pH" = 3,.75 + log( (0.50color(red)(cancel(color(black)("M"))))/(0.27color(red)(cancel(color(black)("M")))))#
#"pH" = 3.75 + 0.268 = color(green)(4.02)#
Indeed, the pH of the buffer is higher than the