Balance the following chemical equations:

____ Mg +____ O2 →____ MgO

____ Al +_____O2 → ____ Al2O3

___ MgO +___ CaS → ____ MgS +_____ CaO

____ N2 +___O2 →_____ NO

____Ti3N +____ MgO →_____ Mg3N2 + ____ Ti2O