Hydrogen gas reacts with oxygen to produce water. if a student fills a 250-ml flask with hydrogen at stp. what volume of oxygen is necessary for the reaction

The balanced equation for the above reaction is;

2H₂ (g) + O₂ - - > 2H₂O

Stoichiometry of H₂ to O₂ is 2:1

This means that the molar ratio in which H₂ reacts with O₂ is in the 2:1 ratio.

At constant temperature and pressure, number of moles are directly proportional to volume of gas. Therefore volume ratio in which H₂ reacts with O₂ is 2:1.

volume of 2 mL of H₂ reacts with 1 mL of O₂

therefore 250 mL of H₂ reacts with - 1/2 x 250 = 125 mL

volume of 125 mL of O₂ is required for the reaction