The mass number of an atom is determined by ___. 1.adding the protons and electrons
2.adding the protons and neutrons
3.adding the electrons and neutrons
4. adding the protons, electrons and neutrons

Answerδh > 0explanationc₆h₆  (s)  → c₆h₆ (l)if you are changing it from a solid to a liquid, you are pretty much melting the solid. this requires heat energy. therefore, the reaction is endothermic (takes in energy); the system enthalpy increases as the reaction proceeds: δh > 0.

Self-ionizes to form an equilibruium system in which [ h_{3} o^{+} ]=[ oh^{-} ]=10^{-7} m

A)  it is neutral because the concentration of hydronium ions equals that of hydroxide ions