Determining pH using the Henderson-Hasselbalch Equation
Calculating the pH for a Ratio of Amine to Ammonium Ion
The pH at which the ratio of amine to ammonium ion will be 1 to 100 is approximately -0.4. To determine the pH at which the ratio of amine to ammonium ion will be 1 to 100 using the Henderson-Hasselbalch equation, we need to use the pKa values and the equation: pH = pKa + log ([A-]/[HA]),
where [A-] is the concentration of the deprotonated form (amine) and [HA] is the concentration of the protonated form (ammonium ion).
Given the pKa values:
pKa1 = 1.6 (for HN-CH-0-OH),
pKa2 = 9.6 (for CH CEO OH),
pKa3 = 3.6.
To have a ratio of 1 to 100 between amine and ammonium ion, we want [A-]/[HA] = 1/100.
Let's assume the concentration of the amine is C and the concentration of the ammonium ion is 100C.
Using the Henderson-Hasselbalch equation, we have:
1/100 = 10^(pH - pKa),
where pKa is the pKa value for the relevant reaction.
Rearranging the equation, we have:
pH - pKa = log(1/100) = -2.
Substituting the pKa value into the equation, we have:
pH - 1.6 = -2,
pH = -2 + 1.6,
pH = -0.4.
Therefore, the pH at which the ratio of amine to ammonium ion will be 1 to 100 is approximately -0.4.
Using the Henderson-Hasselbalch equation, determine at what pH the ratio of amine to ammonium ion will be 1 to 100. The pH at which the ratio of amine to ammonium ion will be 1 to 100 is approximately -0.4.