Final answer:
After refilling a 10,000 gallon pool with slightly less chlorinated water (0.001% chlorine) at a rate of 5 gallons per minute for 1 hour, the concentration of chlorine in the pool is expected to remain approximately the same as the initial 0.01%, because only a small fraction of the pool's total volume has been diluted.
Step-by-step explanation:
The student asked what will be the chlorine concentration in the pool after 1 hour if a swimming pool with 10,000 gallons at 0.01% chlorine concentration is refilled with water at 0.001% chlorine concentration at a rate of 5 gallons per minute, with the pool also draining at the same rate.
To solve this, we must recognize that the chlorine concentration in the pool is progressively being diluted with lower-concentration chlorine water. Refilling and draining the pool at the same rate will lead to a decrease in concentration. After 1 hour, which is 60 minutes, 5 gallons per minute times 60 minutes equals 300 gallons will have been replaced. This is 3% of the total volume of the pool water which initially had a higher concentration of chlorine.
Since the dilution is very small relative to the total volume of the pool (10,000 gallons), the change in concentration will not be significant. Therefore, the concentration of chlorine in the pool after 1 hour will remain closest to the initial concentration of 0.01% (option b).