Which is not true about pH?
a. pH is representative of the concentration of hydrogen ions
b. pH can indicate the acidity or alkalinity of a substance
c. if the pH of a solution changes from 7 to 6, this indicates a 10 fold increase hydrogen
d. pH 7 is the midpoint of the scale and indicates equal amounts of hydrogen and hydroxide
e. a solution with a pH of 9 is acidic

e. a solution with a pH of 9 is acidic

Explanation:

The pH scale shows the degree of acidity or alkalinity of a substance. The scale is graduated from 0-14. pH of 0-6.9 shows acidity, 7 is the midpoint of the scale and indicates neutrality. 8-14 shows alkalinity. An increase or decrease of pH by one digit indicates a ten fold increase or decrease in hydrogen ion concentration. From the foregoing, a pH of 9 can never indicate acidity.

aquifers are bounded above and below by impermeable rock. the driving force of groundwater movement in confined aquifers is pressure, rather than gravity.