Place whole number coefficients in the blanks to balance the chemical reaction. h2o --> h2 + o2

It will be
H2O》H2 + (1/2)O2.

Spontaneity tell us the direction of the reaction, but not how fast it goes. gibbs free energy brings together enthalpy, entropy and temperature in one easy formula. g = h - ts. and, finally the sign of delta g is always negative for a spontaneous reaction.