Why can't silver have a mass number of 107.87?

Sulfuric acid is a polyprotic acid. write balanced chemical equations for the sequence of reactions that sulfuric acid can undergo when it's dissolved in water.

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.

Describe at least two advantages and two disadvantages of using hydropower as a source of energy.