Calculate Ka of a 0.10 M solution of lactic acid has a pH of 2.44
Lactic acid has one acidic hydrogen. A 0.1 M solution of lactic acid has a pH of 2.44. Calculate Ka for lactic acid? When we do acid/base questions, we always need to ask ourselves 2 questions.
Question1 Do we have an acid or a base?
In this case the question itself, told us that we are dealing with an acid.
Question 2 Is this a weak or a strong acid?
Strong acids are: HCl - hydrochloric acid HNO3 - nitric acid H2SO4 - sulfuric acid (HSO4- is a weak acid) HBr - hydrobromic acid HI - hydroiodic acid HClO4 - perchloric acid HClO3 - chloric acid
Our acid does not belong to this list and is therefore a weak acid.
For weak acids, we must always do ICE charts. Before the ice chart, we should write the reaction. Generic reaction of dissociation of a weak acid is HA -- H+ + A- We plug all the values in our ice chart to see the equilibrium values, which are .1-x, x and x. Since we are given the pH, we can calculate [H+], since it is equal to 10^-pH. This calculation gives us the equilibrium concentration of H+ or x. Plugging our value into the x, we can easily calculate Ka.
Please contact Transformation Tutoring with any of your chemistry needs. We tutor chemistry online, in Brooklyn, and Manhattan. Our chemistry tutors love to help our students ace their classes.