Open Question
The Kb of hydroxylamine, NH2OH, is 1.10 * 10^-8. A buffer solution is prepared by mixing 100.0 mL of a 0.36 M hydroxylamine solution with 50.0 mL of a 0.26 M HCl solution. Determine the pH of the resulting solution.
Ch.17 - Aqueous Ionic Equilibrium
Chapter 17, Problem 134
What is the mass of sodium formate required to be dissolved in 250.0 cm³ of a 1.4 M formic acid solution to prepare a buffer solution with a pH of 3.36?
Verified step by step guidance1
Identify the components of the buffer solution: formic acid (HCOOH) and sodium formate (HCOONa).
Use the Henderson-Hasselbalch equation for buffer solutions: \( \text{pH} = \text{pK}_a + \log \left( \frac{[\text{A}^-]}{[\text{HA}]} \right) \), where \([\text{A}^-]\) is the concentration of the conjugate base (sodium formate) and \([\text{HA}]\) is the concentration of the acid (formic acid).
Look up or calculate the \(\text{pK}_a\) of formic acid. It is typically around 3.75.
Rearrange the Henderson-Hasselbalch equation to solve for \([\text{A}^-]\): \([\text{A}^-] = [\text{HA}] \times 10^{(\text{pH} - \text{pK}_a)}\).
Calculate the moles of sodium formate needed using the concentration \([\text{A}^-]\) and the volume of the solution (250.0 cm³ or 0.250 L), then convert moles to mass using the molar mass of sodium formate.
Related Practice
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A 0.867-g sample of an unknown acid requires 32.2 mL of a 0.182 M barium hydroxide solution for neutralization. Assuming the acid is diprotic, calculate the molar mass of the acid.
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Textbook Question
A 25.0-mL volume of a sodium hydroxide solution requires 19.6 mL of a 0.189 M hydrochloric acid for neutralization. A 10.0-mL volume of a phosphoric acid solution requires 34.9 mL of the sodium hydroxide solution for complete neutralization. Calculate the concentration of the phosphoric acid solution.
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Open Question
What relative masses of dimethylamine and dimethylammonium chloride are needed to prepare a buffer solution with a pH of 10.43?
Open Question
You are asked to prepare 2.0 L of an HCN/NaCN buffer that has a pH of 9.8 and an osmotic pressure of 1.35 atm at 298 K. What masses of HCN and NaCN should you use to prepare the buffer? (Assume complete dissociation of NaCN.)
Textbook Question
What should the molar concentrations of benzoic acid and sodium benzoate be in a solution that is buffered at a pH of 4.55 and has a freezing point of -2.0 °C? (Assume complete dissociation of sodium benzoate and a density of 1.01 g/mL for the solution.)
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