10 vol. H2O2 means 1 vol (in mL or L ) of H2O2 will give 10L (or 10mL ) of oxygen O2 at NTP/STP. Now, ∵10 vol. of O2 is given by −1 volume of H2O2 ∴500 vol. of O2 is given by =
500×1
10
=50 vol Thus, 50mL of H2O2 is required to get 500mL of O2 at NTP/STP and option (c) is the correct answer.