How is the sign of the voltage for an overall reaction connected to whether or not a reaction will take place

Can someone me with these questions plz.

What happens when an atom of sulfur combines with two atoms of chlorine to produce sci2? a. each chlorine atom shares a pair of electrons with the sulfur atom. b. an electron is transferred from each chlorine atom to the sulfur atom. c. an electron is transferred from the sulfur atom to each chlorine atom. d. each chlorine atom shares all its valence electrons with the sulfur atom.

Which change to the system wood cause the freely-moving piston to lower?