Multiple Choice
Calculate the pH of a solution formed by mixing 200 mL of a 0.400 M C2H5NH2 solution with 350 mL of a 0.450 M C2H5NH3+ solution. (Kb of C2H5NH2 is 5.6 x 10 -4).
18. Aqueous Equilibrium
Intro to Buffers
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The addition of which of the following would destroy a 1.0 L buffer that is 0.50 M HC2H3O2 and 0.40 M NaC2H3O2?
A
15.0 g HCl
B
0.50 moles HC2H3O2
C
20.0 g NaC2H3O2
D
0.20 moles NaOH
E
all of the above
Verified step by step guidance1
Understand the concept of a buffer solution: A buffer solution resists changes in pH when small amounts of acid or base are added. It typically consists of a weak acid and its conjugate base.
Identify the components of the buffer: In this problem, the buffer consists of acetic acid (HC2H3O2) and sodium acetate (NaC2H3O2). The concentrations are 0.50 M for HC2H3O2 and 0.40 M for NaC2H3O2.
Consider the effect of adding strong acids or bases: Adding a strong acid like HCl or a strong base like NaOH can overwhelm the buffer capacity, leading to a significant change in pH.
Calculate the moles of HCl added: Convert the mass of HCl (15.0 g) to moles using the molar mass of HCl (approximately 36.46 g/mol). Use the formula: \( \text{moles} = \frac{\text{mass}}{\text{molar mass}} \).
Compare the moles of HCl to the buffer capacity: Determine if the moles of HCl added exceed the buffer's ability to neutralize the added acid. If the moles of HCl are greater than the moles of the buffer components, the buffer will be destroyed.
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