What quantity of electrons (in mole) is lost when one mole of iron (ll) ions is oxidized to iron (lll) ions?

The common feature of reactions at the anode is that

From the following equations, what is the order of decreasing reactivity of X, Y and Z? Y _(s) + X²⁺_(aq) → Y^{2+_(aq) + X_(s) X_(s) + Z2+_(aq) → X2+_(aq) + Z_(s)}

What is the value of x in the following equation? MnO- ₄ + 4H⁺ + xe- → MnO ₂ + 2H₂O

If the value of ∆H for a reaction is negative, it means that the reaction is