I'm currently studying for the MCAT and most of the physics questions I get wrong, the explanations adequately help me. But, one question has me stumped. "Question:" What is the standard emf for the galvanic cell in which the following overall reaction occurs? 2Na(s) + Cl2(g) -> 2Na+(aq) + 2Cl–(aq) Half-reaction (V) E° red Na+(aq) + e– -> Na(s) –2.71 Cl2(g) + 2e– -> 2Cl–(aq) +1.36 A) –1.35 V B) +1.35 V C) +4.07 V D) +6.78 V "end of question" The answer they provide is: According to the table, the oxidation of Na has a potential of +2.71 V and the reduction of Cl2 has a potential of +1.36 V. The standard emf for the galvanic cell is therefore +2.71 V + 1.36 V = +4.07 V. Thus, C is the best answer. My understanding was, to calculate the emf, I would have needed to double the charge during the reduction of sodium because 2 moles are used in the cell. But the Kaplan test clearly claims that the reduction of sodium is only counted once. Why is this? I chose D) +6.78 V I'm tired of getting 12 every time I write the physics section practice, it's my weakest. I want better. No, I'm not taking any silly expensive study courses to help me.