A new potential heart medicine, code-named X-281, is being tested by a pharmaceutical company, Pharma-pill. As a research technician at Pharma-pill, you are told that X-281 is a monoprotic weak acid, but because of security concerns, the actual chemical formula must remain top secret. The company is interested in the drug's value because only the dissociated form of the chemical is active in preventing cholesterol buildup in arteries. To find the of X-281, you prepare a 0.079 test solution of X-281. The pH of the solution is determined to be 3.00. What is the of X-281?
HA ==>H^+ + A^-
Ka = (H^+)(A^-)/(HA)
Convert pH of 3.00 to (H^+).
Plug in that value for (H^+) and (A^-) and for (HA) plug in 0.079-(H^+). solve for Ka, then for pKa. Post your work if you get stuck.
You need to re-read your post an fill in the missing blanks. For example, two lines from the bottom:
To fin the ???????of X-281, you ......
So it would help if we knew what we were looking for. Another example, last line:
What is the ?????of X-281?
A new potential heart medicine, code-named X-281, is being tested by a pharmaceutical company, Pharma-pill. As a research technician at Pharma-pill, you are told that X-281 is a monoprotic weak acid, but because of security concerns, the actual chemical formula must remain top secret. The company is interested in the drug's Ka value because only the dissociated form of the chemical is active in preventing cholesterol buildup in arteries.
To find the pKa value of X-281, you prepare a 0.079M test solution of X-281. The pH of the solution is determined to be 3.00. What is the pKa of X-281?
Is the concentration of A^- just 0.079 then?
To find the pKa value of X-281, we can use the Henderson-Hasselbalch equation:
pH = pKa + log([A-]/[HA])
In this case, X-281 is a monoprotic weak acid, which means it donates one proton (H+) when it dissociates. Therefore, we can assume that [A-] represents the concentration of the dissociated form of X-281 (acid's conjugate base) and [HA] represents the concentration of the undissociated form (acid).
Given that the pH of the test solution of X-281 is 3.00, we can substitute these values into the equation:
3.00 = pKa + log([A-]/[HA])
Now, we need to determine the ratio of [A-]/[HA]. However, we don't have the exact concentrations of [A-] and [HA]. Instead, we are given the concentration of the test solution of X-281, which is 0.079 M. Because we can assume that the acid dissociates very little, we can consider the concentration of [HA] as approximately the initial concentration of X-281 (0.079 M). Since X-281 is a weak acid, its dissociation would be small compared to its initial concentration.
Hence, the ratio of [A-]/[HA] is [A-]/0.079.
We can substitute this ratio into the Henderson-Hasselbalch equation:
3.00 = pKa + log([A-]/0.079)
Now, we can rearrange the equation to solve for pKa:
pKa = 3.00 - log([A-]/0.079)
However, we still don't have the exact value of [A-] to substitute into the equation. In this case, it seems we need additional information or experimental data to accurately determine the pKa value of X-281.