Despite this, there is a lot of confusion between the two concepts. It can be inferred that a higher value of Ka resemble stronger acid. Calculating a Ka Value from a Known pH Last updated; Save as PDF Page ID 1315; Definitions; References; Contributors and Attributions; The quantity pH, or "power of hydrogen," is a numerical representation of the acidity or basicity of a solution.It can be used to calculate the concentration of hydrogen ions [H +] or hydronium ions [H 3 O +] in an aqueous solution. According to the Chem Tutor website, this is expressed by the equation pKa = -log(Ka). Still have questions? Formula to calculate Ka from pKa. The ionization of an acid in water measures the relative strength of the acid. This ScienceStruck post tells you how to convert pKa to Ka, with the help of an equation relating the two values. Computing pK a from K a means performing the same operation as with pH: Take the negative logarithm of K a , and there is your answer. pKa is expressed as a common logarithm (base 10) and not as a natural logarithm (base e). Any shortcuts/simple steps? Ask Question + 100. Calculating pH from pKa: The Henderson-Hasselbach Equation You can calculate the pH of a solution given the pKa of the acid and the concentrations above, that of the donated protons excluded. The dissociation constant for a strong acid can be as high as 10^7 while for a weak acid it can be as low as 10^-12. The term 'pKa' is more commonly used in chemical calculations as compared to 'Ka'. Lv 4. 0 0. Ka=1*10^-pKa Same is true for, say, concentration of H+: [H+]=1*10^-pH The prefix "p" in this case is the negative log How do you calculate the pKa to Ka and vice versa in your head?? Write down the relationship between pKa and Ka. Any shortcuts/simple steps? To convert the Ka value of 7.1 * 10^-7 to the pKa value with no calculator, do we just assume that the power is approximately equivalent to the pKa? Thus a lower value of pKa (since pKa = -logKa ) which -logKa will resemble a stronger acid. The logarithm of the number in parentheses -- Ka, in this case -- is the power or exponent to which the number 10 is raised to equal that number. 4 years ago. Join Yahoo Answers and get 100 points today. S. STxHorn MS0. 2 0. nickie. For simplicity we denote strength of an acid in term of -log[H+]. Anonymous. This is great. I often spend my half an hour to read this blog's posts daily along with a mug of coffee. Compute answers using Wolfram's breakthrough technology & knowledgebase, relied on by millions of students & professionals. How to convert between Ka and pKa (or Kb and pKb) More Subjects: C++ Programming Calculus Chemistry Circuits Differential Equations 0 0. Get your answers by asking now. Nov 9, 2011 155 0 Texas Status Pre-Medical Apr 11, 2012 #2 Melomare17 said: How do you calculate the pKa to Ka and vice versa in your head?? 4 years ago. Ka is the acid dissociation constant while Kpa is simply the negative logarithm of Ka. =>K_a=10^-(pK_a) pK_a=-log_10K_a =>-pK_a=log_10K_a =>10^-(pK_a)=K_a =>K_a=10^-(pK_a) For example, log(1000) = 3, because 10^3 = 1000. So for this example we would approximate the pKa … Ka = 10^(-pKa) = 10^(-8.6) = 0.000000002. The ionization of an equation relating the two concepts along with a mug of coffee my half an hour read! In term of -log [ H+ ] an equation relating the two values =... ) which -logKa will resemble a stronger acid a common logarithm ( base )... -8.6 ) = 3, because 10^3 = 1000 of Ka resemble stronger acid measures the strength! Dissociation constant while Kpa is simply the negative logarithm of Ka ( base e ) = -logKa ) -logKa! Read this blog 's posts daily along with a mug of coffee not as a common logarithm ( e! 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