A student added zinc powder to copper sulfate in a polystyrene cup and used the data she collected to calculate the enthalpy change of the reaction when 1 mole of copper sulfate reacts with 1 mole of zinc. However, she found that her value was lower than the published data for this reaction. Suggest two reasons why this might be.

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.