Ответ:

Dano:

m(CoO)=25g

____________

V(H2)-?

H2+CoO=Co+H2O

M(CoO)=59g/mol+16g/mol=75g/mol

M(H2)=2g/mol

m(H2)=2g*25g/75g=0.6g

n(H2)=0.6g/2g/mol=0.3mol

V(H2)=0.3ml*22.4l/mol=6.72l