碳鋅電池及鹼性電池內，為何鋅筒當正極，而不是碳棒當正極？

You may refer to the reactions which occur at the cathode and anode.

cathode: 2NH4＋　＋ 2e- ---＞ 2NH3 H2

anode: Zn －＞ Zn2＋ ＋ 2e-

From the above eqt., We can see that cathode is positive electrode while anode is the negative electrode.

Conventional current flows in the opposite direction of the e- flow.
Therefore, the electode gives out e- is positive electrode.


碳棒不會發生任何反應嗎？

In addition, Carbon electrode is inert. It does not involve in the reaction.
It is widely accepted to consider the carbon electrode as inert electrode, which does not involve in any reaction.

鋅是金屬,有電子作電離
而碳是非金屬,沒有電子,不能電離
因為要成閉合電路,need電子
so一定係鋅筒當正極