What is the answer for question 17 and what is mean by "number of electrons for complete discharge?"

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Which of the following needs the largest number of electrons for complete discharge during an electrolysis process?
a) 3 mol of $\ce{Al^{3+}}$
b) 4 mol of $\ce{Al^{3+}}$ ions
c) 5 mol of $\ce{OH^-}$ ions
d) 7 mol of $\ce{O^{2-}}$ ions


$$\text{a)} 3\times+3 = 9$$ $$\text{b)} 4\times+3 = 12$$ $$\text{c)} 5\times-1= -5$$ $$\text{d)} 7\times-2 = -14$$ This seems like an ambiguous question.

  • b) "needs" the most electrons supplied to become neutral
  • d) "gives up" more electrons than b) to become neutral.

I'd have to take "needs" literally and go with b) as the answer.

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