Hydrogen and oxygen react chemically to form water. How much water would form if 4.8 grams of hydrogen reacted with 38.4 grams of oxygen?
We need a stoichiometric equation for water synthesis:
Clearly, dihydrogen must be present in a 2:1 molar ratio with respect to dioxygen.
Given these molar quantities (they are approx. 2:1) the gases are present in stoichiometric proportion.
Do you think that this would be an exothermic reaction; i.e. do you think that energy would be released by the reaction?