Please help!

Consider the reaction of hydrogen and oxygen to form water as follows:

2 H2 (g) + O2 (g) --> 2 H2O (l)

if 10.5 g of hydrogen are placed in a reaction vessel, how many grams of oxygen are required to fully react with the hydrogen to make water? Numerical answers only; do not include units in your answer!

Nitric acid can be formed in two steps from the atmospheric gases nitrogen and oxygen, plus hydrogen prepared by reforming natural gas. in the first step, nitrogen and hydrogen react to form ammonia: (g) (g) (g) in the second step, ammonia and oxygen react to form nitric acid and water: (g) (g) (g) (g) calculate the net change in enthalpy for the formation of one mole of nitric acid from nitrogen, hydrogen and oxygen from these reactions. round your answer to the nearest .