Answer which the as 114. The space shuttle environmental control system handles

Question

Answer which the as 114. The space shuttle environmental control system handles excess CO, (which the astronauts breathe out; it is 4.0% by mass of exhaled air) by reacting it with lithium hydroxide, LiOH, pellets to form lithium carbonate, Li COs, and water. If there are seven astronauts on board the shuttle, and each exhales 20. L of air per minute, how long could clean air be generated if there were 25,000 g of LiOH pellets available for each shuttle mission? Assume the density of air is 0.0010 g/mL.

Explanation / Answer

Per minute, 20L of air is exhaled, per person. There are 7 people, hence total 7×20L = 140L per minute

Density of air = 0.001g/mL; Mass percent of CO2 in air = 4%

Mass of air exhaled per minute = volume × density = (140 × 1000) ml × 0.001g/mL = 140g

Amount of CO2 exhaled = 4% of 140 = 0.04×140 = 5.6g

Now reaction of LiOH and CO2 is

2 LiOH + CO2 -------> Li2CO3 + H2O

1 mole of CO2 = 2 moles of LiOH

44g of CO2 = (2×24)g of LiOH

5.6g of CO2 = (48×5.6) / 44 = 6.109g of LiOH

Hence 6.109g of LiOH is consumed per minute

25000g of LiOH is consumed in 25000/6.109 = 4092.26 minutes

60 minutes is one hour;

4092.26 minutes = 4092.26/60 = 68.2 hrs

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