In the equilibrium system
CH 3 COOH(aq) + H 2 O(l) ⇌ H 3 O + (aq) + CH 3 COO – (aq)
which of the following species is present in the highest concentration?
a. CH 3 COOH
b. H 3 O +
c. CH 3 COO –
d. The concentrations of CH 3 COOH, H 3 O + and CH 3 COO – are equal.

15. which of the following is not human-caused groundwater pollution? a. water in an aquifer dissolves elements such as arsenic and mercury from surrounding rock. b. water in an aquifer is contaminated by leachate that seeps into the ground from a landfill. c. water in an aquifer becomes polluted with chemicals used in hydraulic fracturing, or fracking. d. water in an aquifer absorbs harmful bacteria from the drainage field of a septic tank.