Well, it is possible to predict the amounts of the products. But you're using an ionic chemical equation without the spectator ions, so you'll have to write a different one. Also, since you're conduction this in aqueous solution, at the end of the reactoin, all you have is ions in solution ... so technically, you won't have any K2SO4 and MnSO4, unless you evaporate the water, but that is a solubility problem.