Question 1

Basic chemistry: atomic mass of oxygen (standard isotope)  For elemental oxygen, identify the standard atomic mass used for O in calculations (approximate integer). Choose the correct value.

Accepted Answer

Concept The atomic mass of oxygen is approximately 16 u for the common isotope O-16. (Note: 32 u refers to the molecular mass of O2.) Final Answer 16

Question 2

Fuel technology: production of coal gas — true or false  Statement: “Coal gas is obtained by mixing coal and gas at ambient conditions.” Decide whether this statement is correct.

Accepted Answer

Concept Coal gas (town gas) is obtained by the destructive distillation of coal (or by carburation processes), not by mixing coal with an existing gas at ambient conditions. Final Answer No

Question 3

IC engines (SI/petrol): typical compression ratio range  For conventional petrol (spark-ignition) engines, select the typical compression ratio range used in practice. Choose the correct range.

Accepted Answer

Concept SI (petrol) engines commonly operate with compression ratios ≈ 6:1–10:1. Among the given ranges, 5 to 8 best fits standard textbook values and avoids knock for regular fuels. Final Answer 5 to 8

Question 4

Polytropic/thermodynamic processes: special case n = 0 in p vⁿ = C  Given p vⁿ = constant, identify the process when n = 0. Choose the correct process name.

Accepted Answer

Concept/Approach For p vⁿ = C, putting n = 0 gives p v⁰ = p = constant, which defines a constant pressure (isobaric) process. Final Answer constant pressure process

Question 5

Air-standard Diesel cycle: effect of cut-off ratio on efficiency  For a fixed compression ratio, how does the thermal efficiency of the Diesel cycle vary with the cut-off ratio? Choose the correct trend.

Accepted Answer

Concept Diesel cycle efficiency (for fixed compression ratio) decreases as the cut-off ratio rc increases, because more heat is added at higher temperatures with less effectiveness. Thus, η increases as rc decreases. Final Answer decrease in cut-off

Question 6

Stoichiometry: CO formation from C with limited oxygen  Given: 1 kg of carbon requires 4/3 kg of oxygen to form carbon monoxide (CO). Compute the mass of CO produced. Choose the correct value.

Accepted Answer

Concept/Approach Reaction: 2C + O2 → 2COMolar masses: C=12, O2=32, CO=28. Step-by-step 24 kg C + 32 kg O2 → 56 kg COFor 1 kg C: O2 needed = 32/24 = 4/3 kg (given)CO produced = 56/24 = 7/3 kg. Final Answer 7/3 kg

Question 7

Perfect (ideal) gas behavior: governing gas laws  Identify which classical gas laws collectively govern the behavior of a perfect gas through the ideal gas relation. Choose the correct option.

Accepted Answer

Concept Boyle’s (p ∝ 1/V at constant T), Charles’ (V ∝ T at constant p), and Gay-Lussac’s (p ∝ T at constant V) together synthesize into the ideal gas equation pV = nRT. Final Answer all of these

Question 8

Thermodynamics: definition of specific heat at constant volume (cᵥ)  Identify what we call the heat required to raise the temperature of a unit mass of a gas by one degree when the volume is held constant. Choose the correct option.

Accepted Answer

Concept The specific heat at constant volume, denoted cv, is defined as the heat required per unit mass per degree temperature rise when the volume is kept constant. Why not others? cp (specific heat at constant pressure) applies when pressure is constant; 'kilo Joule' is a unit of energy, not a definition. Final Answer specific heat at constant volume

Question 9

Thermodynamic cycles: nature of Stirling and Ericsson cycles  Classify the Stirling and Ericsson cycles by reversibility and idealization. Choose the correct option.

Accepted Answer

Concept Ideal Stirling and Ericsson cycles are composed of isothermal and isochoric/isobaric processes with perfect regeneration. In the idealized sense, they are reversible cycles, achieving Carnot efficiency between the same temperature limits. Final Answer reversible cycles

Question 10

Kinetic theory of gases: formula for the most probable molecular speed  Select the correct expression for the most probable speed of gas molecules in terms of absolute temperature T and molar mass M (or Boltzmann constant k and molecular mass m). Ch…

Accepted Answer

Concept From the Maxwell–Boltzmann distribution for molecular speeds, the characteristic speeds are: Most probable speed: vmp = √(2RT/M) = √(2kT/m) Mean (average) speed: v̄ = √(8RT/(πM)) RMS speed: vrms = √(3RT/M) Verification (units) R (J/mol·K), T (K), M (kg/mol) ⇒ RT/M has units m²/s²; square root gives m/s. Common pitfalls Do not confuse vmp with vrms (factor 3) or with v̄ (factor 8/π). Final Answer vmp = √(2RT/M)

Question 11

Definition check: what do we call a sequence of processes returning to initial state?  A series of operations that occurs in a fixed order and restores the system to its initial state at the end. Choose the correct term.

Accepted Answer

Concept A thermodynamic cycle is any sequence of processes that starts and ends at the same thermodynamic state. A cycle may be idealized as reversible or consist of real (irreversible) processes; the definition itself is the closed path on a property diagram. Final Answer thermodynamic cycle

Question 12

Fuel gas production: true/false statement about water gas formation  Statement: “Water gas is obtained by passing air and a large amount of steam over waste coal at about 650°C.” Decide whether this statement is correct.

Accepted Answer

Concept Water gas (CO + H2) is produced by passing steam over red-hot coke (typically near 1000°C). Air is not used during the water-gas reaction stage because oxygen would burn carbon to CO2, lowering CO yield. Air–steam mixtures over fuel beds yield producer gas or semi-water gas, not pure water gas. Final Answer False

Question 13

Gas constants: select the correct SI value for the specific gas constant of air  Pick the correct numerical value (with units) commonly used for the gas constant of air in SI calculations. Choose the correct option.

Accepted Answer

Concept The specific gas constant for air is Rair ≈ 287 J/(kg·K). (The universal gas constant is 8.314 kJ/(kmol·K) = 8314 J/(kmol·K).) Final Answer 287 J/kg·K

Question 14

Town (street/domestic) lighting/heating gas — historical usage  Identify which manufactured gas was mostly used historically for street and domestic lighting and heating in towns. Choose the correct option.

Accepted Answer

Concept Coal gas (also called town gas) was widely used in urban distribution networks for lighting and heating before natural gas adoption. Final Answer Coal gas

Question 15

Temperature scales: absolute zero reference on Celsius and Fahrenheit scales  Select the correct value that represents absolute zero temperature. Choose the correct option.

Accepted Answer

Concept Absolute zero is 0 K, which corresponds to approximately −273.15 °C (commonly taken as −273 °C in rounded form) and −459.67 °F. Final Answer −273°C

Question 16

Properties of water: standard specific heat value (approximate)  Choose the standard textbook value for the specific heat of liquid water near room temperature. Choose the correct option.

Accepted Answer

Concept The specific heat capacity of liquid water is approximately c ≈ 4.187 kJ/(kg·K) near 15–20 °C. Notes 2512 is close to the latent heat of vaporization per kg expressed in kJ/kg divided by a factor, not the specific heat. Final Answer 4.187

Question 17

Petroleum processing: identify the separation method described  Process description: evaporate and condense the component with the lowest boiling point first, then the next higher, and so on, recovering liquid fuels separately in order of boiling po…

Accepted Answer

Concept The described stepwise separation by boiling points is fractional distillation, using a fractionating column to draw products at different temperature levels (e.g., gasoline, kerosene, diesel, etc.). Why not others? Cracking chemically breaks larger hydrocarbons into smaller ones; carbonisation produces coke by heating coal in absence of air; 'full distillation' is not a standard process term. Final Answer fractional distillation

Question 18

Thermal engineering (fuels): identify the incorrect statement about fuels  Options compare properties of liquid and solid fuels and desirable fuel characteristics. Choose the single incorrect statement from the list.

Accepted Answer

Concept/Approach Typical gross calorific values: gasoline/petrol ≈ 44–46 MJ/kg; diesel ≈ 42–46 MJ/kg; coal ≈ 24–35 MJ/kg. Thus, liquids are usually higher than common solids. Fuels are predominantly hydrocarbons. For many practical uses a fuel that lights readily (not excessively high ignition temperature) is desirable; some texts say “moderate to low” ignition temperature. Why C is incorrect Statement C reverses the usual trend: solid fuels typically have a lower calorific value than liquid fuels. Final Answer Solid fuels have higher calorific value than liquid fuels.

Question 19

Fluid mechanics basics: select the correct pressure relation  Definitions: Absolute pressure, Gauge pressure, Atmospheric pressure. Choose the correct equation relating these three.

Accepted Answer

Concept/Approach By definition: pabs = patm + pgauge. Final Answer Absolute pressure = Gauge pressure + Atmospheric pressure

Question 20

Thermodynamics: work in a free expansion process  A gas expands freely against vacuum (no external resistance) from one volume to a larger volume. What is the work done by the gas in free expansion?

Accepted Answer

Given Free expansion: external pressure = 0. Concept/Approach Boundary work: W = ∫ pext dV. In free expansion, pext = 0 ⇒ W = 0. Final Answer Zero

Thermodynamics Questions