Chapter: Chapter 13: Water: A Limited Resource
Quantitative Questions
1. Calculate how many gallons of water are wasted each year from a leak of one drop per second (13,140 drops equals 1 gallon).
a) 1 gallon
b) 360 gallons
c) 2400 gallons
d) 13,140 gallons
e) 31,536,000 gallons
Ans: c
Response: 1 drop per second * 60 seconds per minute * 60 minutes per hour * 24 hours per day * 365 days per year = 31,536,000 drops per year. 31,536,000 drops per year / 13,140 drops per gallon = 2400 gallons per year
Feedback: 14.6
Difficulty: Easy
2. At a particular site, the ocean water used for desalination has a salinity of 35 ppt (parts per thousand). If the desalinization was able to remove all of the salt from water, how many grams of salt will be removed in the process of producing 100 liters of fresh water?
1 liter of fresh water weighs 1 kg; ppt = weight of solute / weight of solution * 1000; note that the weight of the solute is included in the weight of the solution.
a) 100 kg
b) 42 kg
c) 36.27 kg
d) 3.627 kg
e) 3.627 g
Ans: d
Response:
100 liter * 1 kg /liter = 100 kg
35 ppt = 35 / 1000
35 / 1000 = x / (100 kg + x), multiply both sides by 1000
35 = 1000x / (100 kg + x), multiply both sides by (100 kg + x)
35(100 kg + x) = 1000x
3500 kg + 35x = 1000x
3500 kg = 1000x – 35x
3500 kg = 965x
x = 3500 kg / 965
x = 3.627 kg (approximate)
Feedback: 14.5
Difficulty: difficult
3) Access to 20L (5.2 gal) of clean water per day is considered adequate. A typical American uses nearly 150L (40 gal) of water per day. If the current U.S. population is approximately 303,484,000 million, calculate how much excess water per day (in both liters and gallons) Americans consume above the standard daily required amount.
a) 39.4 billion L/day, 10.5 billion gal/day
b) 39.4 billion L/day, 10.5 million gal/day
c) 39.4 million L/day, 10.5 billion gal/day
d) 3.9 billion L/day, 10.5 million gal/day
e) 3.9 million L/day, 10.5 million gal/day
Ans: a
Response: In liters/day: 150 L/day – 20 L/day = 130 L/day * 303,484,000 people = 39,452,920,000 L/day for the entire population
In gallons/day: 40 gal/day – 5.2 gal/day = 34.8 gal/day * 303,484,000 people = 10,561,243,200 gal/day for the entire population
Feedback: 14.1
Difficulty: Easy
4) The 1922 Colorado River Compact stipulates an annual allotment of 7.5 million acre-feet of water to the lower Colorado (California, Nevada, Arizona, and New Mexico). An acre-foot equals approximately 326,000 gallons of water. If the standard adequate daily requirement of water is 5.2 gallons per person per day, approximately how many people can this allotment provide for on a daily basis? Approximately, how many people can it provide for if typical American water consumption is 40 gallons per day?
a) 1.2 billion, 1.67 billion
b) 1.2 billion, 167 million
c) 120 million, 1.67 billion
d) 120 million, 167 million
e) 12 million, 1.67 million
Ans: b
Response: 7,500,000 million acre-feet * 326,000 gallons = 2,445,000,000,000 gallons / 365 days = 6,698,630,136 gallons/day.
Standard water consumption: 6,698,630,136 gallons per day / 5.2 gallons per person per day = 1,288,198,103 people
Typical American water consumption: 6,698,630,136 gallons per day / 40 gallons per person per day = 167,465,753 people
Feedback: 14.3
Difficulty: Medium
5) Today, ultra low flush toilets are being sold that only use 1.6 gallons per flush. Most post-1980 toilet models use 3.5 gallons per flush. Calculate the annual percent reduction in toilet water use for a family of four if a typical family member flushes 4 times per day.
a) 56.2%
b) 25.6%
c) 54.3%
d) 36.5%
e) none of the above
Ans: c
Response:
Flushes per family per day: 4 * 4 = 16, therefore 16 times per day per family
Gallons used per day with typical model toilet: 3.5 * 16 = 56, therefore 56 gallons per day per family - 56 * 365 = 20,440 gallons per year
Gallons used per day with ultra-low flush toilet: 1.6 * 16 = 25.6, therefore 25.6 gallons per day per family – 9,344 * 365 = gallons per year
Annual percent reduction: 20,440 – 9,344 = 11096/20,440 = 54%
Feedback: 14.6
Difficulty: Easy
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