Question

'X' is a metal, on heating metal 'X' with oxygen forms compound 'Y' which will be black in colour on passing hydrogen gas through compound 'Y', metal 'X' and water is obtained.
X+O2--Y
Y+H2--X+H2o

Answer 1

X is copper (Cu)

Cu+O2=CuO(black substance)

CuO+H2=Cu+H2O

Therefore,

X=Cu

Y=CuO