Describe why the amount of Lithium hydroxide present limits the amount of time the astronauts can spend in space?
2LiOH(s) + CO2(s) -> Li2CO3(s) +H2O(l)
CO2 is produced every time a person exhales, some NASA spacecraft rely on this rection to remove exhaled CO2 from the air inside the aircraft. Air is pumped through a filter containing LiOH. Inside the filter, CO2 from the air when it reacts with LIOH to produce Lithium Carbonate.
In the movie "Apollo 13", the trip to the moon was jeopardized because the astronauts lost one of their oxygen tanks due to an electrical malfunction. Everything about the time the astronauts were able to spend on this journey revolved around correct amounts of live-giving substances, such as oxygen, being available. One of the problems they encountered while trying to survive was rising carbon dioxide levels in the space modules they were traveling in.
The reaction you describe is one of the solutions to the problem of rising carbon dioxide levels within the confines of a space suit or artificial environment. Lithium hydroxide will quite readily combine with carbon dioxide gas to produce lithium carbonate and liquid water. Within the confines of the space capsule, however, there is a limited amount of space readily available to store the lithium hydroxide needed. So, just like the astronauts of Apollo 13 found out, we are limited by the amount of raw material we have available. If the amount of raw material available changes, the amount of time available to be spent in space changes also.
By the way, if you've never seen the movie, it is a tremendous teaching tool regarding this very question. At every twist and turn, it is made obvious that going to the moon isn't like taking a spin around the block in your car. If you run out of gas, you can't just get out and walk to the nearest gas station. Things that are taken for granted here on Earth, such as breathing oxygen in and exhaling carbon dioxide, must be accounted for in the limited parameter of the space vehicle itself. Apollo 13 was called a "successful disaster", in that every one associated with that effort overcame the limitations placed upon them; they did not get to the moon, but they did get all three astronauts back to Earth, safe and sound.