Question

Ca + O2 => a
a +   H2O => b
b + c => e + d
d+ f => NaOH + H2
H2 + g => H2O

Answer 1

2Ca+O2=2CaO
a=CaO
Cao+H2O=Ca(OH)2
b=Ca(OH)2
H2+O2=H2O
g=O2
H2O+Na=NaOH+H2
d=H2O
f=Na
Ca(OH)2+H2=Ca+H2O
e=Ca
c=H2