Chemistry
Chemistry
Problem
Equal volumes of 0.010 M HCl are separately added to two beakers: one contains 1.00 L of pure water (initial pH = 7.00), and the other contains 1.00 L of a solution that is 0.10 M in both CH₃COOH and CH₃COO⁻. Which of the following predictions about the resulting pH changes is most accurate? a) The buffer’s pH will rise slightly while the pure water’s pH falls, because removes nearly all of the added . b) Both solutions will experience about the same decrease in pH because each receives the same concentration of added . c) The pH of the pure water will drop by roughly 2 units, whereas the buffer’s pH will drop by far less than 1 unit because neutralizes most of the added . d) The buffer’s pH will fall more than the water’s pH because the weak acid component releases additional into the solution.Intuitive explanation
When you add a strong acid like HCl to pure water versus a buffer solution, you're testing how well each resists pH change. Pure water has no species to neutralize the added , so the pH drops dramatically. The second solution is a buffer—a mixture of a weak acid and its conjugate base—which can absorb added by having the acetate ions react with it, keeping pH relatively stable. The key insight is that buffers work by shifting equilibrium rather than being overwhelmed, so the pH change will be much smaller in the buffered solution.
Intuitive explanation
When you add a strong acid like HCl to pure water versus a buffer solution, you're testing how well each resists pH change. Pure water has no species to neutralize the added , so the pH drops dramatically. The second solution is a buffer—a mixture of a weak acid and its conjugate base—which can absorb added by having the acetate ions react with it, keeping pH relatively stable. The key insight is that buffers work by shifting equilibrium rather than being overwhelmed, so the pH change will be much smaller in the buffered solution.