【Daily Question】May 4, 2018: Participation +2 Wealth； +3 to +10 wealth for correct answers
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Fill-in-the-blank: There is a mixed gas of H2 and N2 with a volume of 50 mL. After burning it in air, the volume decreases by 15 mL. What is the volume percentage of H2 in the mixed gas? ( ) 20%
At this point, it is necessary to determine the state of the water produced by combustion. If the water is in the form of water vapor, then the volume decrease is equivalent to the volume of oxygen that participated in the reaction; the volume of hydrogen is 30 mL, accounting for 60% of the total volume of the mixed gas； If the water is in liquid form, then the decrease in volume is equivalent to the sum of the volumes of hydrogen and oxygen involved in the reaction; the volume of hydrogen is 10 mL, accounting for 20% of the total volume of the gas mixture.