Q:

Balancing simple Redox equation

How would you balance these two redox equations? Would you add a '2' in front of Pt2+ and a '2' in front of H+ ?

A:

Oxidation is loss of electrons and reduction is gain of electrons,so in these equations platinum and cadmium lost 2 electrons(oxidation) which Hydrogen ions used to form Hydrogen gas(reduction).
The redox is as follows
$$\ce{Pt -> Pt^{2+} + 2e-}$$
$$\ce{2H+ +2e- -> H2}$$
So the net equation is 
$$\ce{Pt +2H+ -> Pt^{2+} + H2}$$
You can check that out
http://www.chemguide.co.uk/inorganic/redox/equations.html

