Final answer:
The coefficient that needs to be put in front of the O (oxygen) to balance the equation H4 + O → 2H2O is 1, when the coefficient in front of H2 is adjusted to 2, giving the balanced equation 2H2 + O2 → 2H2O.
Step-by-step explanation:
To balance the chemical equation given as H4 + O → 2H2O, we need to adjust the coefficients so that there are equal numbers of each type of atom on both sides of the equation. Initially, the equation is not balanced because there are 4 hydrogen atoms on the left but only 2 hydrogen atoms (from the 2 water molecules) on the right. Similarly, there is 1 oxygen atom on the left and 2 on the right. To balance the equation, we must change the coefficient of H₂ from 1 to 2 in front of the reactant H₂, and place a coefficient of 2 in front of the product H₂O. When we balance the equation, it becomes 2H₂ + O₂ → 2H₂O. This satisfies the law of conservation of mass, where the number of atoms for each element is the same on both sides of the equation. The coefficients represent a 2:1:2 ratio of hydrogen, and oxygen to water, respectively, which is the simplest whole-number ratio for balancing this equation.