Final answer:
The difference in hydrogen ion concentration between pH 4.0 and pH 5.5 is that the solution with pH 4.0 has approximately 31.6 times higher concentration than the solution with pH 5.5, due to the logarithmic nature of the pH scale.
Step-by-step explanation:
The difference in hydrogen ion concentration between a solution with a pH of 4.0 and one with a pH of 5.5 can be calculated using the relationship that a pH difference of 1 corresponds to a tenfold difference in hydrogen ion concentration. Since the pH scale is logarithmic, moving from a pH of 4.0 to 5.5 entails a difference of 1.5 pH units. Therefore, we can calculate the difference in hydrogen ion concentration as follows:
Understanding and utilizing the concept of pH and its relationship to hydrogen ion concentration is essential in fields like chemistry, as it helps predict the acidity or alkalinity of a solution.