A large Kb value indicates the high level of dissociation of a strong base. Enter the pKa value into the calculator and divide by 2. how to convert ph to pka calculate ph with pka how to find ph from pka when is ph = pka ph equation with pka how to convert pka to ph from pka to ph pka to ph relationship pka to ph converter ka to ph converter ka to pka converter relation between pka and ph ph=pka+log(base/acid) ph to pka converter calculating pka from ph ph=pka+log(a-/ha) What is this absorbance? Let’s identify what we know to be true about the system: 1. Method 1 Include activity coefficients in the calculations. Chemistry Stack Exchange is a question and answer site for scientists, academics, teachers, and students in the field of chemistry. Answer: The pH of the given solution is 4.94. The Ka value for most weak acids ranges from 10-2 to 10-14. Convert pKb to Kb: Kb = 10^-pKb = 10^-4.74 = 1.82 x 10^-5. Since the absorbance is higher in basic solution, we might conclude that $\ce{Ind-}$ is observed. Is it safe to assume that the basic solution only contains $\ce{Ind-}$, while in buffered solution $\ce{HInd}$ is present as well? Postdoc in China. Because of the way the log function works, a smaller pKa means a larger Ka. pKa = pH + log [HA] / [A-] This tells us that when the pH = pK a then log [HA] / [A-] = 0 therefore [HA] = [A-] ie equal amounts of the two forms. The pKa of phosphate buffer can be calculated by using a mathematical expression. Do you know which kind of buffer it is? Problem #1. The pKa is the pH at which the system consists of an equimolar concentration of the proton donor (CH3COOH) and proton acceptor (CH3COO¯). They describe the degree of ionization of an acid or base and are true indicators of acid or base strength because adding water to a solution will not change the equilibrium constant. Problem #2: A 0.128 M solution of uric acid (HC 5 H 3 N 4 O 3) has a pH of 2.39. Lets call this amount “mol HAi” 2. Calculate the pKa of lactic acid, when the concentration of lactic acid and lactate are 0.020M and 0.073M respectively. Like pH and pOH, these values also account for hydrogen ion or proton concentration (for Ka and pKa) or hydroxide ion concentration (for Kb and pKb). Term to describe paradox where those with less subject matter expertise can sometimes make better teachers? I'm confused. What is the basic solution? pH=4.6 and pKa=8.6 Since it is a weakly acidic drug, let’s apply the following formula. If we wanted to find the pKa for methanol, all we have to do is take the Ka and take the negative log of it. When calculating pH from pKa and pKb values, how do you know which value to use. 2) You are given the concentration and K b (or pK b) of a base, then asked to calculate the pH.. If the absorbance of one of the buffer solutions (pH = 4.623) was 0.319 and the absorbance of the basic solution was 0.625, what is the $\mathrm{p}K_\mathrm{a}$ of the indicator? Whenever you see a "p" in front of a value, like pH, pKa, and pKb, it means you're dealing with a -log of the value following the "p". Calculate the K a of uric acid. Because you calculate pKa with this formula (pKa = -log(Ka)), and since Ka is the acid dissociation constant (meaning that its value doesn't change for a certain acid), the value then can be taken as a literature value, and the errors in those are not required to be propagated. [ ] [ ] log HA A pH pKa − = + Where [A-] is conjugate base and [HA] is conjugate acid This equation is often used to determine the proportion of conjugate base [A-] and of conjugate acid [HA] one must use to attain a particular pH value of a buffer.