Question

Difficulty: HardUnit Conversions

An industrial water filtration system filters water at a constant rate of 0.5 liters per second0.5\text{ liters per second}. The system consumes a chemical powder at a rate of 2.5 milligrams2.5\text{ milligrams} per gram of impurities removed from the water. If the water contains an average of 0.12 grams0.12\text{ grams} of impurities per liter, how many grams of the chemical powder does the system consume during 4 hours4\text{ hours} of continuous operation?

Answer: 2.16 grams

Answer

The system consumes 2.16 grams2.16\text{ grams} of chemical powder during the 44 hours of operation.
The correct answer is 2.162.16. First, convert the 44 hours of continuous operation into seconds: 4×3,600=14,4004 \times 3,600 = 14,400 seconds. Next, multiply this duration by the filtration rate to find the total water filtered: 14,400×0.5=7,20014,400 \times 0.5 = 7,200 liters. Multiply the volume by the impurity concentration to find the total mass of impurities: 7,200×0.12=8647,200 \times 0.12 = 864 grams. Then, find the mass of chemical powder consumed: 864×2.5=2,160864 \times 2.5 = 2,160 milligrams. Finally, convert milligrams to grams by dividing by 1,0001,000, resulting in 2.162.16 grams.

Step-by-Step Solution

1
Convert the operating time from hours to seconds.
14,400 seconds14,400\text{ seconds}
Since the filtration rate is given in liters per second, the total operating time must be converted from hours to seconds to align units. There are 3,6003,600 seconds in one hour.
2
Calculate the total volume of water filtered during the operation.
7,200 liters7,200\text{ liters}
Multiply the operating time in seconds by the filtration rate of 0.50.5 liters per second.
3
Calculate the total mass of impurities removed from the filtered water.
864 grams864\text{ grams}
Multiply the total volume of filtered water by the concentration rate of 0.120.12 grams of impurities per liter.
4
Determine the mass of chemical powder consumed in milligrams.
2,160 milligrams2,160\text{ milligrams}
Multiply the total mass of impurities in grams by the consumption rate of 2.52.5 milligrams of chemical powder per gram of impurities.
5
Convert the mass of chemical powder from milligrams to grams.
2.16 grams2.16\text{ grams}
Divide the mass in milligrams by 1,0001,000 because there are 1,0001,000 milligrams in one gram.

Key Concept

Dimensional analysis and multi-step unit conversion involving rates
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