Which statement is true of a chemical change?
OA.
It involves changes in the molecular structure.
OB.
It involves changes in phase but not changes in the molecular structure.
(
C.
It involves dissolving one substance into another.
OD.
It involves a change in the state, or phase, of a substance.
E.
It involves the process of separating two or more dissolved substances.

Which of these expressions are correct variations of the combined gas law? p1v1t2 = p2v2t1 both

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.

How does the value of the equilibrium constant show that a reaction reaches equilibrium very quickly? (a) the equilibrium constant is large. (b) the equilibrium constant is small. (c) the equilibrium constant is zero. (d) the value of the equilibrium constant does not show how quickly a reaction comes to equilibrium.