The equation is: 2H2 + O2 ---> 2H2O
In the chemical reactions the coefficients means number of unit formulas or number of moles.
So, the right interpretation is that 2 unit formulas of diatomic hydrogen react with 1 unit formula of diatomic oxygen to form two unit formulas of water.
That is equivalent to say that 2 moles of H2 (diatomic hydrogen) react with 1 mol of O2 (diatomic oxygen) to form 2 moles of H2O (water).
One wrong interpretation would be assume that the stoichiometric coefficients of the reaction are the same for grams. It is not.
This would be such wrong interpretation "Two grams of hydrogen react with one gram of oxygen to form two grams of water." It woul cause Shana to make a mistake.
