FE Environmental practice questions with answers

Answer: D) 35 years

For continuous exponential growth, the doubling time is ln 2 divided by the growth rate: 0.693/0.02 ≈ 35 years.

• AIncorrect. ln(1.5)/0.02 ≈ 20 years is the time for the population to grow by 50%, not to double.
• BIncorrect. 1/0.02 = 50 leaves out the ln 2 factor. For continuous growth, t = ln 2 / r.
• CIncorrect. ln 3/0.02 ≈ 55 years is the tripling time, not the doubling time.
• DCorrect. Setting N/N₀ = e^(rt) = 2 gives t = ln 2 / r = 0.693/0.02 ≈ 34.7 years.

Answer: C) 0.0025

• AIncorrect. That's at least one.
• BIncorrect. That's adding; multiply for both.
• CCorrect. 0.05 × 0.05.
• DIncorrect. Both months must exceed.

Answer: C) Refuse and explain the hazard

• AIncorrect. That conceals a hazard.
• BIncorrect. Safety overrides that.
• CCorrect. Public safety comes first.
• DIncorrect. Only licensed engineers can seal.

Answer: B) $5,526

For a uniform series of end-of-period deposits, the future worth is F = A(F/A, i, n) = $1,000 × 5.526 = $5,526.

• AIncorrect. This adds the five deposits and ignores the interest they earn while in the account.
• BCorrect. These are end-of-year deposits, so F = A(F/A, 5%, 5) = $1,000 × 5.526 = $5,526.
• CIncorrect. This treats the deposits as made at the start of each year (an annuity due): 5,526 × 1.05 ≈ $5,802. The deposits here are made at the end of each year.
• DIncorrect. This compounds the full $5,000 as one lump sum over 5 years (5,000 × 1.2763). Most deposits earn interest for less than 5 years, and the last earns none.

Answer: A) 0.40 g cells/g substrate

The yield coefficient is cells produced per unit of substrate consumed: Y = 50/125 = 0.40 g cells/g substrate.

• ACorrect. Yield = mass of cells produced ÷ mass of substrate consumed = 50/125 = 0.40 g/g.
• BIncorrect. This is substrate consumed ÷ cells produced (125/50), which is the inverse of the yield.
• CIncorrect. This is (125 - 50)/125, the fraction of substrate not turned into cells. It is not the cells produced per unit of substrate.
• DIncorrect. This divides the cells by the sum of cells and substrate (50/175). Yield uses only the substrate consumed as the denominator.

Answer: D) Bicarbonate, carbonate and hydroxide

• AIncorrect. That doesn't contribute.
• BIncorrect. Those don't neutralize acid.
• CIncorrect. That isn't alkalinity.
• DCorrect. Bicarbonate usually dominates near neutral pH.

Answer: B) Repeated or long-duration exposure, often over months or years

Chronic toxicity comes from repeated or long-duration exposure, and its effects may appear only after a long latency period. Acute toxicity comes from a single or short-term exposure.

• AIncorrect. This describes acute toxicity: the ability of a chemical to cause harm after a single exposure.
• BCorrect. A chronically toxic substance causes damage after repeated or long-duration exposure, or causes damage that appears only after a long latency period. Carcinogens are an example.
• CIncorrect. This describes the LD50, which is a measure of acute lethality after a single dose. It is not a definition of chronic toxicity.
• DIncorrect. Exposures of days to weeks are short-term (acute or subchronic) exposures. Chronic toxicity involves long-term, repeated exposure, often for a large part of the lifetime.

Answer: C) D^2.63

• AIncorrect. It grows faster than D.
• BIncorrect. It grows faster than D.
• CCorrect. Capacity rises sharply with diameter.
• DIncorrect. Larger pipes carry more.

Answer: C) 2

• AIncorrect. Longer pipe means more loss.
• BIncorrect. It's linear in L.
• CCorrect. Head loss is proportional to L.
• DIncorrect. Loss depends on length.

Answer: A) 100 days

• ACorrect. τ = V/Q = 10⁸/10⁶ days.
• BIncorrect. That's inverted.
• CIncorrect. Recheck the powers of ten.
• DIncorrect. Recheck the powers of ten.

Answer: A) Sorb strongly to soil and move slowly

• ACorrect. Its retardation factor is high.
• BIncorrect. It sorbs strongly.
• CIncorrect. Koc describes sorption.
• DIncorrect. It prefers organic carbon.

Answer: A) 40 m³/(m²·day)

• ACorrect. Q/A = 2,000/50.
• BIncorrect. That's inverted.
• CIncorrect. Divide, don't multiply.
• DIncorrect. Recheck: 2,000/50.

Answer: C) Consuming alkalinity

• AIncorrect. It consumes alkalinity.
• BIncorrect. Denitrification recovers some.
• CCorrect. It uses about 7.1 mg as CaCO₃ per mg of ammonia-N; low alkalinity can stall nitrification.
• DIncorrect. It lowers pH.

Answer: B) Nitrogen oxides and volatile organic compounds react photochemically in sunlight

Ground-level ozone is a secondary pollutant. It forms when NOx and VOCs, mostly from burning fossil fuels, react in sunlight.

• AIncorrect. Ground-level ozone is a secondary pollutant. Combustion sources emit its precursors, mainly NOx and VOCs, not ozone itself.
• BCorrect. Ozone forms when NOx and VOCs react in sunlight, so levels peak on hot, sunny afternoons downwind of traffic and industry.
• CIncorrect. Chlorine from CFCs destroys ozone in the stratosphere. It does not form ozone at ground level.
• DIncorrect. Sulfur dioxide oxidizing in droplets forms sulfate, which causes acid rain and fine particles. It is not an ozone formation pathway.

Answer: A) Directly above the liner

• ACorrect. It drains leachate to sumps before it builds head on the liner.
• BIncorrect. That would let leachate reach the liner first.
• CIncorrect. That's for stormwater.
• DIncorrect. It sits at the base.