When acid or base is added to water, the #pH# changes dramatically. Why, when acid or base is added to a buffer solution, does the #pH# change only marginally?

Answer 1

Because in distilled water, the effect of added acid/base is unmoderated. Buffers act to resist gross changes in #pH#.

A buffer contains a weak acid and its conjugate base in appreciable quantities. The #pH# of the buffer is reasonably close to the #pK_a# of this weak acid.

Using the buffer equation, we can recognize this characteristic:

#pH = pK_(a) + log_10{([A^-])/([HA])}#
At undergraduate level, you should be able to derive this equation. When the concentration of the acid is equal to that of the conjugate base, #log_10{([A^-])/([HA])}# #=# #log_10(1)# #=# #0#, so #pH = pK_a#.
In an unbuffered solution, added hydroxide or protium ion is free to express its concentration, and dramatic rises/falls in #pH# occur. In the buffered solution, added protium ion protonates the base #A^-#, but this increase in #[HA]# is moderated by the logarithmic term. Capisce?
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Answer 2

Buffer solutions resist changes in pH because they contain a weak acid and its corresponding conjugate base. The equilibrium between the acid and its conjugate base helps neutralize added acid or base, minimizing pH fluctuations.

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Answer 3

When acid or base is added to a buffer solution, the pH changes only marginally because the buffer system resists changes in pH. This resistance is due to the presence of a weak acid and its conjugate base, or a weak base and its conjugate acid, in the buffer solution. When an acid is added to the buffer solution, the weak base in the buffer reacts with it to form its conjugate acid, limiting the increase in hydrogen ions and thus maintaining the pH relatively stable. Similarly, when a base is added, the weak acid in the buffer reacts with it to form its conjugate base, preventing a significant decrease in hydrogen ions and keeping the pH relatively constant. This ability of the buffer solution to resist changes in pH is a result of the equilibrium established between the weak acid and its conjugate base (or weak base and its conjugate acid) in the solution.

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Answer 4

When an acid or base is added to a buffer solution, the pH changes only marginally because the buffer solution contains a weak acid and its conjugate base or a weak base and its conjugate acid. These components react with any added acid or base, minimizing the change in pH by maintaining a relatively constant concentration of hydrogen ions (H+) or hydroxide ions (OH-) through the process of neutralization. This occurs due to the equilibrium established between the weak acid and its conjugate base (or weak base and its conjugate acid), which resists significant changes in pH by absorbing or releasing protons as needed to counteract the effects of the added acid or base.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

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