18. Aqueous Equilibrium

A 270.0 mL buffer solution initially contains 3.0×10⁻² M of HCHO₂ and 3.0×10⁻² M of NaCHO₂. To adjust the buffer pH to 4.10, should you add NaOH or HCl to the buffer mixture?

A buffer consists of 0.120 M HNO2 and 0.150 M NaNO2 at 25 °C. The pKa of HNO2 is 3.40. What is the pH of the buffer?

A buffer solution has 0.625 M HCN and 0.575 M CN⁻. If 0.030 mol of HCl is added to 400. mL of the buffer solution, what is the pH after the addition? The pKa of hydrocyanic acid is 9.23.

Using the Henderson-Hasselbalch equation, what is the pH of a buffer solution that is 0.250 M in HCN and 0.170 M in KCN, given that the pKa of HCN is 9.31?

Consider a buffer solution that is 0.50 M in NH3 and 0.20 M in NH4Cl. For ammonia, pKb = 4.75. Calculate the pH of 1.0 L of the solution upon addition of 30.0 mL of 1.0 M HCl to the original buffer solution.

Consider a buffer solution that is 0.50 M in NH3 and 0.20 M in NH4Cl. For ammonia, pKb = 4.75. Calculate the pH of 1.0 L of the solution upon addition of 0.010 mol of solid NaOH to the original buffer solution.

Consider a buffer solution that is 0.50 M in NH3 and 0.20 M in NH4Cl. For ammonia, pKb = 4.75. Calculate the pH of 1.0 L of the solution upon the addition of 30.0 mL of 1.0 M HCl to the original buffer solution.

Use the Henderson-Hasselbalch equation to calculate the pH of a solution that is 0.255 M in CH3NH2 and 0.120 M in CH3NH3Br. The pKa of CH3NH3+ is 10.64.

Using the Henderson-Hasselbalch equation, what can you conclude about the relative concentrations of CH3NH2 and CH3NH3Cl in a buffer solution where the pH is 10.64 and the pKb of CH3NH2 is 3.36?

What is the [CH3CO2-]/[CH3CO2H] ratio necessary to make a buffer solution with a pH of 4.44? Ka = 1.8 × 10^-5 for CH3CO2H.

What is the pH of a buffer system that has 0.25 M HCN and 0.38 M CN⁻, given that the pKa of hydrocyanic acid is 9.23?

Using the Henderson-Hasselbalch equation, what is the pH of a buffer system that contains 0.87 M dimethylamine ((CH3)2NH) and 0.68 M dimethylammonium ion ((CH3)2NH2+)? The Kb of dimethylamine is 5.9 × 10⁻⁴.

What mass of CH3COONa must be added to create 300.0 mL of a buffer solution with a pH of 5.00 and a CH3COOH concentration of 0.100 M? The pKa of acetic acid is 4.75.

What mass of KNO2 must be added to create 200.0 mL of a buffer solution with a pH of 3.00 and an HNO2 concentration of 0.150 M? The pKₐ of nitrous acid is 3.34.