Textbook Question
Is the pH greater than, equal to, or less than 7 after the neutralization of each of the following pairs of acids and bases? (a) NaOH and benzoic acid (C6H5CO2H)
18. Aqueous Equilibrium
Intro to Acid-Base Titration Curves
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A buffer solution is prepared by adding 10.0 g of ammonium chloride (NH₄Cl) to 250 mL of 1.00 M NH₃ solution. What is the pH of the resulting buffer solution?
A
5.75
B
7.00
C
9.25
D
11.00
Verified step by step guidance1
Calculate the moles of NH₄Cl using its molar mass. The molar mass of NH₄Cl is approximately 53.49 g/mol. Use the formula: moles = mass (g) / molar mass (g/mol).
Determine the concentration of NH₄Cl in the solution. Since the volume of the solution is 250 mL (or 0.250 L), use the formula: concentration (M) = moles / volume (L).
Recognize that NH₄Cl is a salt that dissociates completely in water to form NH₄⁺ and Cl⁻ ions. The NH₄⁺ ion will act as the conjugate acid in the buffer system.
Use the Henderson-Hasselbalch equation to find the pH of the buffer solution: pH = pKa + log([base]/[acid]). Here, the base is NH₃ and the acid is NH₄⁺. The pKa of NH₄⁺ is approximately 9.25.
Substitute the concentrations of NH₃ and NH₄⁺ into the Henderson-Hasselbalch equation to calculate the pH. Remember that the concentration of NH₃ is given as 1.00 M.
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