Question

determine the optimum mass ratio of Zn to MnO2 in an alkaline battery

This question is answered on a textbook solution here, but I found the solution to be confusing

Answer 1

An alkaline battery produces electrical energy which is given by the following equation,.

Zn(s) + 2 MnO₂(s) + H₂O(l) --------> Zn(OH)₂(s) + Mn₂O₃(s)

From the above equation we see that , 1mol Zn requires 2 mol MnO₂

Molar mass Zn = 65.39 g/mol

and Molar mass MnO₂ = (54.94+2 x 16) = 86.94g/mol x 2mol = 173.88 g

Now,

65.39 g Zn reacts with 173.88g MnO₂

1 g Zn will react with (173.88g/65.39g ) MnO₂

Therefore,

Mass ratio = Zn : MnO₂ = 1: (173.88/65.39) = 1 : 2.659