A buffer is prepared in which the ratio [H2 PO4^-] /[HPO4^2-] is 3.0 (a) What is the pH of this

step 1 Okay, so we have a buffer system here with dihydrogen phosphate and hydrogen phosphate. We know

A buffer is prepared in which the ratio [H2 PO4^-]...

A buffer is prepared in which the ratio $\left[\mathrm{H}_{2} \mathrm{PO}_{4}^{-}\right] /\left[\mathrm{HPO}_{4}^{2-}\right]$ is 3.0 (a) What is the pH of this buffer? (b) Enough strong acid is added to convert $15 \%$ of $\mathrm{HPO}_{4}{ }^{2-}$ to $\mathrm{H}_{2} \mathrm{PO}_{4}^{-}$. What is the $\mathrm{pH}$ of the resulting solution? (c) Enough strong base is added to make the $\mathrm{pH} 7.00$. What is the ratio of $\left[\mathrm{H}_{2} \mathrm{PO}_{4}^{-}\right]$ to $\left[\mathrm{HPO}_{4}^{2-}\right]$ at this point?

A buffer is prepared in which the ratio $\left[\mathrm{H}_{2} \mathrm{PO}_{4}^{-}\right] /\left[\mathrm{HPO}_{4}^{2-}\right]$ is 3.0
(a) What is the pH of this buffer?
(b) Enough strong acid is added to convert $15 \%$ of $\mathrm{HPO}_{4}{ }^{2-}$ to $\mathrm{H}_{2} \mathrm{PO}_{4}^{-}$. What is the $\mathrm{pH}$ of the resulting solution?
(c) Enough strong base is added to make the $\mathrm{pH} 7.00$. What is the ratio of $\left[\mathrm{H}_{2} \mathrm{PO}_{4}^{-}\right]$ to $\left[\mathrm{HPO}_{4}^{2-}\right]$ at this point?

Key Concepts

Conjugate Acid-Base Pairs

Conjugate acid-base pairs are related chemical species where one form can donate a proton and the other can accept it. In a buffer solution, the weak acid and its conjugate base work together such that when an external acid or base is added, they react to minimize the change in pH, thus stabilizing the solution's acidity or basicity.

Effect of Adding Strong Acid or Base

Adding a strong acid or base to a buffer leads to a shift in the equilibrium between the weak acid and its conjugate base. The strong acid reacts with the conjugate base, while a strong base reacts with the weak acid, changing their concentration ratio. This change, quantified by the Henderson-Hasselbalch equation, determines the new pH of the solution, illustrating the buffer's capacity to mitigate drastic fluctuations in pH.

Buffer Systems

Buffer systems are solutions that resist changes in pH when small amounts of acid or base are added. They consist of a weak acid and its conjugate base (or a weak base and its conjugate acid) working together to neutralize added acids or bases, thereby maintaining a relatively constant pH.

Henderson-Hasselbalch Equation

The Henderson-Hasselbalch equation provides a simplified way to estimate the pH of a buffer by relating the pH to the pKa of the weak acid and the logarithm of the ratio of the concentrations of the conjugate base to the weak acid. This equation is an essential tool for calculating the pH of buffer systems and understanding how changes in the ratio affect the pH.

Transcript

Please give Ace some feedback