Question 79 of 138

A 40 mL of a mixture of H2 and O2 was placed in a gas burette at 18 oC and  1 atm pressure. A spark was supplied so that the formation of water was complete . The remaining pure gas had a volume of 10 mL at 18 oC  and 1 atm pressure. If the remaining gas was H2 , what was the initial mole percentage of H2 in the mixture?

  1. 25%
  2. 50%
  3. 35%
  4. 75%