Determine whether or not the mixing of each pair of solutions results in a buffer. d. 105.0 mL of 0.12 M CH3NH2 ; 110.0 mL of 0.15 M CH3NH3Cl

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Identify the components of the solutions: CH3NH2 is a weak base and CH3NH3Cl is its conjugate acid.

Calculate the moles of CH3NH2: Use the formula \( \text{moles} = \text{volume (L)} \times \text{molarity (M)} \).

Calculate the moles of CH3NH3Cl: Use the same formula \( \text{moles} = \text{volume (L)} \times \text{molarity (M)} \).

Determine if the solution can act as a buffer: A buffer solution contains a weak acid and its conjugate base or a weak base and its conjugate acid in comparable amounts.

Compare the moles of CH3NH2 and CH3NH3Cl to see if they are present in significant amounts to resist changes in pH.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Buffer Solutions

A buffer solution is a system that resists changes in pH upon the addition of small amounts of acid or base. It typically consists of a weak acid and its conjugate base or a weak base and its conjugate acid. In this case, the presence of CH3NH2 (a weak base) and CH3NH3Cl (its conjugate acid) suggests that the mixture could function as a buffer.

Weak Bases and Conjugate Acids

Weak bases are substances that partially ionize in solution, establishing an equilibrium between the base and its conjugate acid. CH3NH2 is a weak base, and when mixed with CH3NH3Cl, it can establish an equilibrium that allows the solution to maintain a relatively stable pH, characteristic of buffer systems.

Henderson-Hasselbalch Equation

The Henderson-Hasselbalch equation is used to calculate the pH of a buffer solution. It relates the pH to the pKa of the weak acid and the ratio of the concentrations of the conjugate base and acid. This equation is essential for determining the effectiveness of the buffer formed by the mixing of CH3NH2 and CH3NH3Cl.

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Henderson-Hasselbalch Equation

Related Practice

Textbook Question

For each solution, calculate the initial and final pH after adding 0.010 mol of NaOH. a. 250.0 mL of pure water b. 250.0 mL of a buffer solution that is 0.195 M in HCHO₂ and 0.275 M in KCHO₂ c. 250.0 mL of a buffer solution that is 0.255 M in CH₃CH₂NH₂ and 0.235 M in CH₃CH₂NH₃Cl

Textbook Question

A 100.0-mL buffer solution is 0.100 M in NH₃ and 0.125 M in NH₄Br. What mass of HCl can this buffer neutralize before the pH falls below 9.00?

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Textbook Question

Determine whether or not the mixing of each pair of solutions results in a buffer. b. 125.0 mL of 0.14 M HF; 195.0 mL of 0.070 M NaOH

Textbook Question

Determine whether or not the mixing of each pair of solutions results in a buffer. c. 55.0 mL of 0.15 M HF; 85.0 mL of 0.10 M NaF

Textbook Question

Determine whether or not the mixing of each pair of solutions results in a buffer. a. 155.0 mL of 0.15 M NH3 ; 175.0 mL of 0.17 M HCl