why is copper sheet but not aluminum sheet that becomes the negative pole after putting copper sheet and aluminum sheet connected with wire into concentrated nitric acid?
it may be that aluminum won't react with concentrated nitric acid.
According to metal reactivity series order table, aluminum has a better metallicity, but it will be passivated soon after contacting concentrated sulfuric acid, and won’t react again. But copper and concentrated sulfuric acid can react continually. So aluminum sheet becomes the positive pole after passivation.
