NCEES FE Environmental · USA · National Council of Examiners for Engineering and Surveying
Original practice questions written to the published syllabus · not past papersNCEES FE Environmental is a licensing and registration exam run by National Council of Examiners for Engineering and Surveying, for candidates in USA. Computer-based at Pearson VUE, 110 questions, 6-hour appointment (5 h 20 min exam time, 25-minute break). Reference handbook supplied on screen.
Source: ncees.org.
Checked against the exam body's published information. Formats and fees change; confirm the current edition there before you book.
The chemistry of water, soil and air that pollution, treatment and climate subjects assume: equilibria, the carbonate system, redox, gas solubility, ozone and smog chemistry. GATE ES Section 2 in full.
Our 17 NCEES FE Environmental questions in this subject: 0 easy, 10 medium, 7 hard, across 7 units.
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
These 10 were written to NCEES FE Environmental and are not shown on any other exam's page.
Hypochlorous acid has a pKa of about 7.5. At pH 6.5, which species dominates and why does it matter?
A. HOCl, about 90 per cent, the far stronger disinfectant
One pH unit below pKa the acid form is about 91%; HOCl is a much more effective disinfectant than OCl⁻, so chlorination works better at lower pH.
A water has total hardness 250 mg/L as CaCO3 and total alkalinity 180 mg/L as CaCO3. What are its carbonate and non-carbonate hardness?
B. Carbonate 180, non-carbonate 70 mg/L as CaCO3
When hardness exceeds alkalinity, carbonate hardness = alkalinity = 180 and non-carbonate = 250 − 180 = 70.
Pure water equilibrates with air containing 420 ppm CO2. Take KH = 10⁻¹·⁴⁷ mol L⁻¹ atm⁻¹ and pKa1 = 6.35, and assume [H⁺] ≈ √(Ka1[H2CO3*]). What is its pH?
D. 5.6
[H2CO3*] = 10⁻¹·⁴⁷ × 420 × 10⁻⁶ = 1.42e-05 M; [H⁺] = √(10⁻⁶·³⁵ × 1.42e-05); pH ≈ 5.6. 7.0 ignores CO2; 4.6 is typical acid rain; 8.3 is the bicarbonate endpoint.
What does a positive Langelier saturation index indicate for a water supply?
A. The water tends to deposit calcium carbonate scale
LSI = pH − pHs; positive means supersaturated with CaCO3 (scaling); negative means undersaturated (aggressive or corrosive).
Using Henry's law in the form C = KH × P, with KH for oxygen = 1.3 × 10⁻³ mol L⁻¹ atm⁻¹ at 25 °C and an oxygen partial pressure of 0.21 atm, what is the saturation concentration of dissolved oxygen?
C. About 8.7 mg/L
C = 1.3 × 10⁻³ × 0.21 = 2.73 × 10⁻⁴ mol/L × 32,000 mg/mol ≈ 8.7 mg/L. 4.4 uses atomic oxygen (16); 41.6 ignores the partial pressure; 162 divides instead of multiplying.
Henry's law can be written C = KH·P or P = H·C. If KH = 1.3 × 10⁻³ mol L⁻¹ atm⁻¹ for O2, what is H in atm L mol⁻¹?
C. About 769 atm L mol⁻¹
H = 1/KH = 1/(1.3 × 10⁻³) ≈ 769 atm L mol⁻¹; the two forms are reciprocals. Confusing them is a common error.
The solubility product of CaF2 is 3.9 × 10⁻¹¹. What is its molar solubility in pure water?
C. 2.1e-04 M
Ksp = s(2s)² = 4s³, so s = (3.9 × 10⁻¹¹/4)^(1/3) ≈ 2.1e-04 M. √Ksp treats it as a 1:1 salt; (Ksp)^(1/3) forgets the 4; Ksp/2 is meaningless.
Which treatment removes phosphorus from wastewater by chemical precipitation?
C. Adding aluminium or iron salts, or lime
Al³⁺ and Fe³⁺ form insoluble phosphates; lime precipitates calcium phosphate. Chlorine disinfects; carbon adsorbs organics.
In a BOD test, 6 mL of wastewater is diluted to 300 mL. Initial DO is 8.6 mg/L and DO after 5 days at 20 °C is 4.1 mg/L. What is the BOD5?
A. 225 mg/L
BOD = (D1 − D2)/P = (8.6 − 4.1)/(6/300) = 4.5/0.02 = 225. 4.5 forgets dilution; 90 uses P = 0.05; 430 uses D1 only.
Why is COD always at least as large as BOD for the same sample?
D. Dichromate oxidises more organics than microbes do
The strong chemical oxidant attacks most organics, while microbes oxidise only biodegradable fractions within 5 days.
This plan follows where our questions actually fall, so the time goes where the marks are likely to be. It is our reading of the syllabus, not the exam body's weighting.
Read the manual chapters for these first and do every worked question you can find on them.
Aim for one sitting per unit, then mixed questions across them.
Learn the definitions, classifications and standard numbers; these units are more often recalled than worked.
Come back to these after a first pass, untimed, and read every explanation, including for the options you rejected.
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