A buffer solution is 0.413 M in HF and 0.237 M in KF. If Ka for HF is 7.2×10-4, what is the pH of this buffer solution?

2.90

Explanation:

Any buffer system can be described with the reaction:

Where is the acid and is the base. Additionally, the calculation of the pH of any buffer system can be made with the Henderson-Hasselbach equation:

With all this in mind, we can write the reaction for our buffer system:

In this case, the acid is with a concentration of 0.413 M and the base is with a concentration of 0.237 M. We can calculate the pKa value if we do the "-Log Ka", so:

Now, we can plug the values into the Henderson-Hasselbach

The pH value would be 2.90

I hope it helps!

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.