Passage VI
When hydrogen and oxygen are mixed under certain conditions, H2O will form. Students did the following experiments to study how H2O forms.
Experiment 1
A thick-walled gas syringe fitted with a sparking device was filled with 20 mL of hydrogen gas (H2) and 10 mL of oxygen gas (O2)，as shown in Figure 1.
The syringe plunger was then locked in place and the gases were sparked. A reaction took place, forming droplets of water. The plunger was then released. The gas in the syringe was allowed to adjust to room temperature and pressure, and the final volume of gas was recorded. The remaining gas, if any, was then analyzed to determine its composition. The procedure was repeated with different volumes of gases, and the results were recorded in Table 1.
Since it is known that equal numbers of molecules of different gases occupy equal volumes at the same pressure and temperature, the following equation was suggested:
2 H2 + O2 → H2O
Experiment 2
In the apparatus shown in Figure 2, a stream of H2 was passed over hot copper oxide (CuO), producing H2O vapor. The vapor was then absorbed by calcium chloride (CaCl2).
The changes in the masses of the tube sections containing the CuO and CaCl2 were used to calculate the mass of CuO reacted and the mass of H2O formed. It was determined that 1 molecule of H2O was produced for every CuO reacted:
CuO + H2 → Cu + H2O
32. If 50 mL of H2 and 50 mL of O2 were reacted using the procedure from Experiment 1, the final volume of O2 would most likely be:
Your Answer is
Correct Answer is J
Explanation
It can be seen from table 1 that the consumption ratio of H2 and O2 is 2:1, so if both gases are 50mL, 25mL of O will be left after the reaction 2