Compared with a pH of 7, a solution of

pH 5 has what times/fraction of the hydrogen
concentration?
1. 1/100
2. nearly the same concentration
3. twice
4.5/7
5. 100 times

pH = -log(H^+).

Since the pH is a log function, the H^+ from 1 pH to the next (either higher or lower) is in steps of 10. That is pH = 2 is 10x weaker than a pH of 1 and 10x stronger than a pH of 3

To determine the times/fraction of the hydrogen concentration in a solution with pH 5 compared to a solution with pH 7, we need to understand the concept of pH and hydrogen concentration.

pH is a measure of the acidity or alkalinity of a solution and is based on the concentration of hydrogen ions (H+). The pH scale ranges from 0 to 14, where pH 7 is considered neutral. Solutions with a pH less than 7 are acidic, while those with a pH greater than 7 are alkaline.

The pH scale is logarithmic, which means that each whole number increase or decrease represents a tenfold change in hydrogen ion concentration. For example, a solution with pH 5 is ten times more acidic (has ten times more hydrogen ions) than a solution with pH 6.

In this case, we are comparing a solution with pH 5 to a solution with pH 7. Since the pH scale is logarithmic, for every whole number increase or decrease, the hydrogen ion concentration changes by a factor of 10. Therefore, the difference in pH between 5 and 7 is 2, indicating a hundredfold difference in hydrogen ion concentration.

So, the correct answer is option 5. A solution with pH 5 has 100 times the hydrogen concentration of a solution with pH 7.