Final answer:
A 1.0-liter aqueous solution with a pH of 5.0 contains 100 times more hydronium ions than a solution with a pH of 7.0, since the pH scale is logarithmic and a change of 1 unit corresponds to a tenfold change in ion concentration.
Step-by-step explanation:
The question concerns the comparison of hydronium ion concentrations in aqueous solutions with different pH levels. To analyze the difference between a pH of 7.0 and a pH of 5.0, we need to understand that the pH scale is logarithmic; a change of 1 unit on the pH scale corresponds to a tenfold change in hydronium ion concentration.
For a solution with a pH of 7.0, which is neutral, the concentration of hydronium ions is 1.0 × 10-7 M. An acidic solution with a pH of 5.0 has a higher concentration of hydronium ions because each unit decrease in the pH value corresponds to a tenfold increase in [H3O+]. So, moving from a pH of 7.0 to a pH of 5.0 (a difference of 2 pH units), the hydronium ion concentration increases by a factor of 10 for each unit decrease in the pH. This means that a pH of 5.0 represents a hydronium ion concentration that is 10 × 10 or 100 times greater than that of a solution with a pH of 7.0.
Therefore, compared to a 1.0-liter aqueous solution with a pH of 7.0, a 1.0-liter aqueous solution with a pH of 5.0 contains 100 times more hydronium ions. Hydroxide ions are not directly mentioned in this comparison, but if they were, their concentration would be 100 times less, as they are inversely related to the concentration of hydronium ions.