To obtain a better approximation of the volume at the equivalence point, you can do a first derivative plot. This plots the change of pH divided by the change in volume versus the volume of NaOH. This shows the change in slope of the titration curve as a function of the added volume of base. Common methods of automated end point detection depend on using the first and second derivatives of the classic "S-shaped" titration curve. The end point usually occurs at the point of maximum deflection, where the absolute value of the first derivative reaches a maximum and the second derivative changes sign. Derivatives can easily be computed by using the finite difference approximation. Given two measurements in a pH vs. Volume plot: (V1, pH1) and (V2, pH2), the derivative is: apH ApH ату ΔΥ = pH₂-pH₁ V2-V1 which is plotted at the point between V2 and V1, or mid = 2 Explain the advantages of using a first derivative plot. 12 10 Mixed vs. Volume NaOH Volume NaOH (mL)

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To obtain a better approximation of the volume at the equivalence point, you can do a first
derivative plot. This plots the change of pH divided by the change in volume versus the
volume of NaOH. This shows the change in slope of the titration curve as a function of
the added volume of base.
Common methods of automated end point detection depend on using the first and second
derivatives of the classic "S-shaped" titration curve. The end point usually occurs at the
point of maximum deflection, where the absolute value of the first derivative reaches a
maximum and the second derivative changes sign. Derivatives can easily be computed by
using the finite difference approximation.
Given two measurements in a pH vs. Volume plot: (V1, pH1) and (V2, pH2), the derivative is:
apH ApH
ату ΔΥ
=
pH₂-pH₁
V2-V1
which is plotted at the point between V2 and V1, or mid
=
2
Explain the advantages of using a first derivative
plot.
12
10
Mixed vs. Volume NaOH
Volume NaOH (mL)
Transcribed Image Text:To obtain a better approximation of the volume at the equivalence point, you can do a first derivative plot. This plots the change of pH divided by the change in volume versus the volume of NaOH. This shows the change in slope of the titration curve as a function of the added volume of base. Common methods of automated end point detection depend on using the first and second derivatives of the classic "S-shaped" titration curve. The end point usually occurs at the point of maximum deflection, where the absolute value of the first derivative reaches a maximum and the second derivative changes sign. Derivatives can easily be computed by using the finite difference approximation. Given two measurements in a pH vs. Volume plot: (V1, pH1) and (V2, pH2), the derivative is: apH ApH ату ΔΥ = pH₂-pH₁ V2-V1 which is plotted at the point between V2 and V1, or mid = 2 Explain the advantages of using a first derivative plot. 12 10 Mixed vs. Volume NaOH Volume NaOH (mL)
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