Question

Question #78c3c

Answer 1

There's not enough data to identify M. It could be any of the group 1 metals (except maybe Lithium). Let's keep calling it M.

Explanation:

Burning in air:
`4M+O_2->2M_2O` so `X=M_2O`

X reacting with water:
`M_2O+H_2O->2MOH` so `Y=MOH`

M reacting with water:
`2M+2H_2O->2MOH+H_2` so `Z=H_2`

Y being heated:
`2MOH->M_2O+H_2O`