As the pH of a system decreases:
the [H+] decreases
the Kw decreases
the [OH-] decreases
all of the above
As the pH decreases the H^+ gets larger.
Kw is a constant and changes only with temperature.
If pH gets smaller, H^+ becomes larger and OH becomes smaller.
Look at (H^+)(OH^-) = Kw.
If H goes up, OH must go down. If OH goes up, H^+ must go down. Kw doesn't move so H or OH must if the other one moves.
so the answer would be OH- decreases
yes
As the pH of a system decreases, the concentration of hydrogen ions ([H+]) increases, not decreases. The pH scale is a logarithmic scale, ranging from 0 to 14, where lower pH values indicate higher concentrations of hydrogen ions and higher acidity.
To determine the effects of decreasing pH on the other factors mentioned, let's examine each one separately:
1. The [H+] decreases: This statement is incorrect. As mentioned earlier, the concentration of hydrogen ions increases as pH decreases. The higher the acidity, the higher the concentration of hydrogen ions.
2. The Kw decreases: The autoionization constant of water (Kw) is defined as the product of the concentrations of hydrogen ions ([H+]) and hydroxide ions ([OH-]) in pure water. At a constant temperature, Kw remains constant. Therefore, the statement "the Kw decreases" is incorrect.
3. The [OH-] decreases: This statement is correct. The concentration of hydroxide ions ([OH-]) decreases as the pH of a system decreases. Since pH is a measure of acidity, a lower pH indicates a lower concentration of hydroxide ions.
Therefore, the correct answer is: "the [OH-] decreases" (option c).