Question

if 10.0 g of hydrogen and 75.0 g of oxygen are exploded together in a reaction tube, how much water is produced? What other gas is found in the reaction tube (besides water vapor) after the reaction, and how much of this gas remains?

Answer 1

First, we write the equation for the reaction:

2H₂ + O₂ = 2H₂O
We find the amount of substance of oxygen and hydrogen:
n(H₂) = m(H₂) / M(H₂)
n(H₂) = 10g/2g/mol = 5 mol
n(O₂) = 75g/32g/mol = 2.34 mol
As seen in excess hydrogen:
the amount of unreacted substance hydrogen = 5 - (2 * 2.34) = 0.3125 mol
m(H₂O) = n(H₂O) * M(H₂O)
Because of a lack of oxygen, it is selected for the calculations:
n(H₂O) = 2.34 mol * 2 = 4.68 mol
M(H₂O) = 18 g / mol
m(H₂O) = 18 g / mol * 4.68 mol = 84.24 g
After reaction, the hydrogen will be:
m(H₂) excess = 0.3125 mol * 2 g / vol = 0.625 g