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If the pH of a solution goes from 8 to 7, this means that the hydrogen ion concentration has:

(1) decreased by 1 mole/liter.

(2) increased by 1 mole/liter.

(3) decreased 10 fold.

(4) increased 10 fold

The pH scale is logarithmic, meaning that a decrease of 1 unit in pH corresponds to a 10-fold increase in hydrogen ion ([H+][H^+][H+]) concentration.

Understanding the Change in pH

  • The pH drops from 8 to 7, meaning the solution is becoming more acidic.
  • A decrease in pH means an increase in [H+][H^+][H+] concentration.
  • Each unit decrease in pH increases [H+][H^+][H+] by a factor of 10.

Analyzing the Options

  1. Decreased by 1 mole/liter → Incorrect (the change is logarithmic, not linear).
  2. Increased by 1 mole/liter → Incorrect (the change is not exactly 1 mole/L, but a 10-fold increase).
  3. Decreased 10-fold → Incorrect (this would happen if pH increased).
  4. Increased 10-fold → Correct (since the pH decreased by 1 unit).

Final Answer:

(4) Increased 10-fold

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