A piece of lithium metal was added to a flask of water on a day when the atmospheric pressure was 757.5 Torr. The lithium reacted completely with the water via the reaction shown below to produce 250.0 mL of hydrogen gas, collected over the water at 23°C.
2Li(s) + 2H2O(l) -> H2(g) + 2LiOH(aq)
(a) What is the partial pressure of hydrogen in the collection flask? (Note that the hydrogen is collected over water so there will be gaseous water in the flask along with the hydrogen. At 23°C, the pressure of gaseous water is 21.07 torr. The total pressure will be equal to that of the atmosphere.)
(b) What mass of lithium metal reacted?