What ratio of C2H3O2- to HC2H3O2 is needed in a solution where the pH=3.85? pKa HC2H3O2 = 4.74
Use the Henderson-Hasselbalch eqution that I've shown below. pH = pKa + log (base)/(acid)
Post your work if you get stuck.
To find the ratio of C2H3O2- to HC2H3O2 needed in a solution with a pH of 3.85, we need to determine the equilibrium concentration of each species.
The pH of a solution is related to the concentration of the acidic species and its conjugate base by the Henderson-Hasselbalch equation:
pH = pKa + log([A-]/[HA])
In this case, HC2H3O2 is the acidic species (HA) and C2H3O2- is the conjugate base (A-).
Given:
pKa HC2H3O2 = 4.74
pH = 3.85
We can rearrange the Henderson-Hasselbalch equation to solve for the ratio [A-]/[HA]:
pH - pKa = log([A-]/[HA])
3.85 - 4.74 = log([A-]/[HA])
-0.89 = log([A-]/[HA])
Now, we can calculate the ratio by taking the antilog (inverse logarithm) of -0.89:
[A-]/[HA] = 10^(-0.89)
Using a calculator, we find that 10^(-0.89) is approximately 0.117.
Therefore, the ratio of C2H3O2- to HC2H3O2 needed in the solution is approximately 0.117.
To find the ratio of C2H3O2- to HC2H3O2 in a solution with a pH of 3.85, you need to consider the Henderson-Hasselbalch equation. The Henderson-Hasselbalch equation is given by:
pH = pKa + log([A-]/[HA])
In this equation, [A-] represents the concentration of the conjugate base (C2H3O2-) and [HA] represents the concentration of the acid (HC2H3O2). Rearranging the equation, we get:
log([A-]/[HA]) = pH - pKa
Now, substitute the given values into the equation. The pKa of HC2H3O2 is 4.74, and the pH is 3.85. The equation becomes:
log([A-]/[HA]) = 3.85 - 4.74
Simplifying further:
log([A-]/[HA]) = -0.89
To get the ratio [A-]/[HA], you need to convert the logarithm into exponential form. This can be done by taking the inverse logarithm (antilog) of both sides. The antilog of -0.89 can be calculated using the base 10 exponential function:
[A-]/[HA] = 10^(-0.89)
Using a scientific calculator or an online calculator, you can find that 10^(-0.89) is approximately 0.1258.
Therefore, the ratio of C2H3O2- to HC2H3O2 needed in the solution is approximately 0.1258.