Question

200 cm³ of hydrogen and 150 cm³ of oxygen are mixed and ignited, as per the following reaction,

\[\ce{2H2 + O2  → 2H2O}\]

What volume of oxygen remains unreacted?

Answer 1

\[\ce{2H2 + O2  → 2H2O}\]

2 V        1V          2V

From the equation, 2V of hydrogen reacts with 1V of oxygen

so 200cm³ of Hydrogen reacts with = `200/2`

= 100 cm³

Hence, the unreacted oxygen is 150 −100 = 50cm³ of oxygen.