Question

Here are two possible reactions. Which one is correct and why is the other one incorrect?

Mn²⁺(aq) + 2HClO(aq) -----> MnO₂(s) + 2Cl^-(aq) + 2H⁺(aq)

Mn²⁺(aq) + HClO(aq) + H₂O(l) -----> MnO₂(s) + Cl^-(aq) + 3H⁺(aq)

Answer 1

There are plenty of ways to solve this... mass balance, energy balance, electorn balance, electrode potentials, free gibbs energy, entropy, etc...

The easiest way is doing an electron chage balance:

Mn2+(aq) + 2HClO(aq) -----> MnO2(s) + 2Cl-(aq) + 2H+(aq)

Charge on the left = +2 +2*0 = +2

Charge on the right = 0+2*(-1) + 2*(1) =-2+2 = 0

There is no balance since lft side is +2 charged and right side is neutrally, 0, charged

For the second equation

Mn2+(aq) + HClO(aq) + H2O(l) -----> MnO2(s) + Cl-(aq) + 3H+(aq)

Charge on the left = +2 +2*0+ 0 = +2

Charge on the right = 0+(-1) + 3*(1) = -1+3 = +2

Both sides are +2 charged, therefore, it is possible to do trhis (there is an electron balance)