Answer:
1. 3H2S + 2HNO3 -----> 2NO + 4H2O + 3S
Explanation:
H2S + HNO3 -----> NO + H2O + S
There are 3 O's on left and only 2 on right so put 2 before NO:
H2S + HNO3 ----> 2NO + H2O + S
Now we have 2 N's on left so put 2 before HNO3:
H2S + 2HNO3 -----> 2NO + H2O + S
4 H's on the left so
H2S + 2HNO3 -----> 2NO + 2H2O + S
That makes 6 O's on left so we write
H2S + 2HNO3 ----> 2NO + 4H2O + S
Now there 8 H's on the right but only 4 on the right so we adjust H2S and S:
3H2S + 2HNO3 -----> 2NO + 4H2O + 3S
Now it balances!
Basically you 'play around' with the quantities of each element in this way.
