Calculate the total volume of the gaseous mixture at the end of the reaction?

30cm³ pf hydrogen at s.t.p combine with 20cm³ of oxygen to form steam according to the following equation 2H2(g) + O2(g) → 2H2O(g). Calculate the total volume of the gaseous mixture at the end of the reaction

A. 50cm³
B. 35cm³
C. 30cm³
D. 25cm³

Correct Answer:

Option B – 35cm³