Answer:
a. 2H2 + O2--> 2H2O
b. 2ZnS +3O2-->2ZnO +2SO2
Step-by-step explanation:
a.
note:
(when you put coefficients before the elements or the compounds you should multiply it by each element and the number that's on its right...
so if it's 2H2O
that is 2xH2 which is 4 hydrogen atoms
and 2 x O which is 2 oxygen atoms )
......
on the left side of the equation
there are two atoms of oxygen
but on the right side there's only one atom
so in order to balance them you have to put 2 as a coefficient for H2O
H2+O2 ->2H2O
so now you have 2 hydrogen atoms on the left side and 4 on the right side
you put 2 as a coefficient for H2
and now
there's 4 hydrogen atoms on both sides
and 2 oxygen atoms on both sides
b.
you do the same here
ZnS + O2 -> ZnO + SO2
2 oxygen atoms ---> 3 oxygen atoms
ZnS + 2O2 -> ZnO + SO2
4 oxygen atoms ---> 3 oxygen atoms
ZnS + 2O2 -> 2ZnO + SO2
4 oxygen atoms ---> 4 oxygen atoms
but
1 Zn ---> 2Zn
2ZnS + 2O2 -> 2ZnO + SO2
2S --> 1S
2ZnS + 2O2 -> 2ZnO + 2SO2
2S--> 2S
but
4O---> 6O
2ZnS + 3O2 -> 2ZnO + 2SO2