NCEES FE Other Disciplines · USA · NCEES
Original practice questions written to the published syllabus · not past papersThe physics and chemistry behind materials, water, fuels and electronics that later engineering subjects assume.
In the exams: NCEES FE Chemistry 5–8 questions; first-year core in the ICAR 6th Deans' Committee B.Tech
How our questions for NCEES FE Other Disciplines spread across the units of Engineering Physics & Chemistry. Difficulty: 25 easy, 36 medium, 18 hard.
| Water chemistry: hardness, pH and treatment | 15 | |
| Fuels and combustion chemistry | 13 | |
| Calorific value of fuels | 13 | |
| Polymers and plastics used in agriculture | 13 | |
| Electrochemistry and batteries | 13 | |
| Corrosion and its control | 12 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
A well water contains, per litre, 162 mg Ca(HCO3)2, 120 mg MgSO4, 111 mg CaCl2 and 58.5 mg NaCl. What are its temporary and permanent hardness, as mg/L CaCO3?
C. Temporary 100, permanent 200
Convert with mass × 50/equivalent weight: Ca(HCO3)2 162 × 50/81 = 100 (temporary); MgSO4 120 × 50/60 = 100 and CaCl2 111 × 50/55.5 = 100 (permanent, total 200). NaCl causes no hardness, so adding 50 for it is wrong; 162 and 231 are raw salt masses, not CaCO3 equivalents.
Rainwater collected from a roof has a hydrogen-ion concentration of 3.2 × 10⁻⁶ mol/L. What is its pH?
D. 5.49
pH = −log10(3.2 × 10⁻⁶) = 6 − 0.505 = 5.49. 8.51 is the pOH; 12.65 uses the natural logarithm instead of base 10. 6.49 uses an exponent of −7 instead of −6.
A liquid fuel contains 84% carbon and 16% hydrogen by mass. Taking air as 23% oxygen by mass, what is the minimum (stoichiometric) mass of air per kg of fuel?
D. 15.3 kg
O2 = (32/12)(0.84) + 8(0.16) = 2.24 + 1.28 = 3.52 kg; air = 3.52/0.23 = 15.3 kg. 3.52 kg is the oxygen alone; dividing by 0.21 uses the volume fraction with a mass basis; 12.5 kg uses 4 instead of 8 kg O2 per kg H. Dividing by 0.21 gives 16.8 kg.
A biogas-fired water heater burns pure methane with 20% excess air. How much air is supplied per m³ of methane (same temperature and pressure; air 21% O2 by volume)?
A. 11.43 m³
Theoretical air = 2/0.21 = 9.52 m³; with 20% excess, actual = 1.2 × 9.52 = 11.43 m³. 9.52 m³ omits the excess; adding 0.2 m³ treats 20% as an absolute amount; 2.40 m³ is the total oxygen supplied, not air. Adding 0.2 m³ gives 9.72 m³.
A batch dryer must remove 1,000 kg of water from paddy. Take 2.5 MJ of heat per kg of water evaporated, an overall furnace-plus-dryer efficiency of 50%, and rice husk with a net calorific value of 13 MJ/kg. About how much husk is burnt?
C. About 385 kg
Heat to water = 1,000 × 2.5 = 2,500 MJ; fuel heat = 2,500/0.50 = 5,000 MJ; husk = 5,000/13 = 385 kg. Ignoring efficiency gives 192; multiplying by it gives 96; inverting the ratio gives an impossible 10400 kg.
When a steel water trough rusts in neutral, aerated water, what is the main cathodic reaction?
B. O2 + 2H2O + 4e⁻ → 4OH⁻
In neutral or alkaline aerated water, dissolved oxygen is reduced to hydroxide at the cathode. Fe → Fe²⁺ + 2e⁻ is the anodic reaction; hydrogen evolution dominates in acid solutions; Fe²⁺ reduction would reverse corrosion.
Which statement correctly distinguishes a thermoplastic from a thermoset?
A. A thermoplastic softens on reheating; a thermoset is cross-linked and does not
Thermoplastics are linear or branched chains held by weak forces and can be re-melted and re-moulded; thermosets cure into a cross-linked network that chars rather than melts. Either type can be made by addition or condensation, and colour has nothing to do with the classification.
Why do greenhouse films and outdoor HDPE pipes contain UV stabilisers or carbon black?
B. Ultraviolet light breaks polymer chains, making plastic brittle unless protected
UV photons have enough energy to break bonds and start photo-oxidation, so unprotected polyolefins crack and embrittle; hindered-amine stabilisers, UV absorbers and carbon black slow this. A greenhouse film must still transmit photosynthetically active light, so stabilisers are not added to block it.
Why is open burning of waste PVC pipe and film on a farm especially harmful compared with burning polyethylene?
B. PVC releases hydrogen chloride and chlorinated compounds as well as smoke
PVC contains about 57% chlorine by mass; burning it gives hydrogen chloride and can form chlorinated organic pollutants, in addition to the smoke all plastics give. Clean combustion to CO2 and water is not what happens in an open fire, and methane is not the characteristic product.
A solar irrigation system needs a 48 V battery bank. How many nominal 2 V lead–acid cells, or 3.2 V lithium iron phosphate cells, must be in series?
A. 24 lead–acid cells or 15 LFP cells
48/2 = 24 lead–acid cells; 48/3.2 = 15 LFP cells. Thirteen cells assumes 3.7 V per cell (a different lithium chemistry); 48 cells uses 1 V per cell.
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