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What is the pH of a solution that contains 0.49M NH₃ (aq) and 0.17M NH₄⁺Cl (aq)?

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Final answer:

To find the pH of a solution containing 0.49M NH3 and 0.17M NH4+Cl, the Henderson-Hasselbalch equation is used, which requires the pKa of ammonia and the concentration ratio of base to conjugate acid.

Step-by-step explanation:

To calculate the pH of a solution containing 0.49M NH₃ and 0.17M NH₄⁺Cl, we can use the Henderson-Hasselbalch equation for a buffer solution. This equation is given by:

pH = pKa + log([A-]/[HA])

For the ammonia-ammonium ion system, NH₃ acts as the base (A-) and NH₄⁺ as the conjugate acid (HA). The pKa for ammonia (πKb for NH₃) can typically be found in tables, and it is approximately 9.25 at 25°C. However, this value can vary slightly depending on the source, so always check the provided value in your coursework or textbook. Using the given concentrations, we can substitute into the equation:

pH = 9.25 + log(0.49/0.17)

The logarithm of the ratio of NH₃ to NH₄⁺ concentrations can be calculated, which will then be added to the pKa to find the pH.

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