C4H9OH (g) + O2 (g) →CO2 (g) + ? H2O (l) what coefficient should be placed in front of H2O to balance the hydrogen atoms?

5

Explanation:

To balance the hydrogen atoms, we check the number of hydrogen on the left side, this is equal to the 10 hydrogen atoms we have in the alkanol.

Now, on the right hand side, we can see we only have two hydrogen atoms in the water molecule. Now, to make equal the number of hydrogen atoms on both sides, we simply multiply the number of hydrogen there by 5 to make it 10 too