Lactic acid is a weak acid found in milk. Its calcium salt is a
s...

Question

Lactic acid is a weak acid found in milk. Its calcium salt is a
source of calcium for growing animals. A saturated solution of
this salt, which we can represent as Ca(Lact)2, has a
[Ca2 + ] = 0.26 M and a pH = 8.78. Assuming the salt is completely
dissociated, calculate the Ka of lactic acid.

Accepted Answer

Hey everyone, we're told that a solution containing magnesium acetate contains 0.16 Mueller of magnesium ions And a ph of 9.12 were asked to calculate the K. A. Of acetic acid first. Let's go ahead and determine the polarity of our acetate ion. And we can do this by taking our 0.16 molar of our magnesium and using our multiple ratios and we can see that we have two moles of our ion per one mole of magnesium. So when we calculate this out, we end up with a total of 0.32 molar acetate ion. Now let's go ahead and create a nice chart. Starting with our reaction, we know that we have our acetate ion and we react this with water and we end up with acetic acid plus our hydroxide ions creating our ice chart. We calculated that we started off with 0.32 moller of our acetate ion. We know that we're going to disregard our water since it is a liquid and we initially had zero of our products for our change. We're going to subtract X from our as T ion. And so we'll end up with 0.32 Mueller -X. And we're going to add X to our products. And since we weren't given our KB let's go ahead and calculate the concentration of our hydroxide ions And we can do this by taking our ph of 9.12. So taking our ph We can solve for r. p. o. h. by doing 14 -9.12 Which will get us to a total of 4.88 to calculate the concentration of our hydroxide ions. We can go ahead and get 10 to the negative 4.88. And this will give us a total of 1.33 times 10 to the -5 moller. And this is going to be our X. Now that we have our X. Let's go ahead and solve for R K. B solving for r K B. We know that it's going to be our products over our reactant. So we have X squared Over 0.32 Molar -X. Plugging in our values for X. We end up with 1.33 times 10 to the negative five molar squared divided by 0.32 molar -1.3, 3 times 10 to the -5 Molar. And when we calculate this out, we end up with a total of 5.55 times 10 to the negative 10 which is our KB. And now going back to our question, we were asked to calculate the K. A. To calculate the K. A. We're going to take our kw and divide it by our KB and we know that our K. W is one point oh times since in negative 14. And dividing this by 5.5, 5 times 10 To the -10. This will get us to a K A of 1.80 times 10 to the -5, which is going to be our final answer. So I hope that made sense and let us know if you have any questions.

Lactic acid is a weak acid found in milk. Its calcium salt is a source of calcium for growing animals. A saturated solution of this salt, which we can represent as Ca(Lact)2, has a [Ca2 + ] = 0.26 M and a pH = 8.78. Assuming the salt is completely dissociated, calculate the Ka of lactic acid.

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