If two acids have the same concentration, which factor most significantly impacts their strength comparison?

When comparing the strength of two acids with the same concentration, the most significant factor is the number of hydrogen ions donated by each acid in solution. This is because acid strength is defined by the extent to which an acid can dissociate in water to release hydrogen ions (H+).

A strong acid will completely dissociate in solution, meaning it will release a greater number of hydrogen ions compared to a weak acid, which will only partially dissociate. Therefore, even if two acids are at the same concentration, the strength comparison hinges on how fully each acid ionizes to produce hydrogen ions. This ability to donate hydrogen ions reflects the acid's strength, making option A the key factor in comparing their strengths.

The other factors, such as temperature, molecular size, and visual indicators like color change in litmus paper, are less directly related to the fundamental definition of acid strength. Temperature can affect the dissociation process but is generally held constant when comparing strong and weak acids. Molecular size might influence properties of acids but not their dissociation ability significantly. Similarly, color changes in litmus paper provide information about acidity but do not quantify the strength of the acid in terms of its ability to donate hydrogen ions.