Here is the previous year question paper of NTPC Assistant Chemist Trainee Exam

1 In a throttling process, the pressure of an ideal gas reduces by 50 %. If Cp and Cv are the heat capacities at constant pressure and constant volume, respectively (ϒ=Cp/Cv), the specific volume will change by a factor of
(A) 2
(B) 21/ϒ
(C) 2(ϒ-1)/ϒ
(D) 0.5

Ans:A

2. If the temperature of saturated water is increased infinitesimally at constant entropy, the resulting state of water will be
(A) Liquid
(B) Liquid – vapor coexistence
(C) Saturated vapor
(D) Solid
Ans:A

3. For an exothermic reversible reaction, which one of the following correctly describes the dependence of the equilibrium constant ( K ) with temperature (T ) and pressure ( P ) ?

(A) K is independent of T and P
(B) K increases with an increase in T and P
(C) K increases with T and decreases with P
(D) K decreases with an increase in T and is independent of P

Ans

4. Water is flowing under laminar conditions in a pipe of length L . If the diameter of the pipe is doubled, for a constant volumetric flow rate, the pressure drop across the pipe

(A) decreases 2 times
(B) decreases 16 times
(C) increases 2 times
(D) increases 16 times

Ans:B


5. The local velocity of a fluid along a streamline can be measured by

(A) Pitot tube
(B) Venturi meter
(C) Rotameter
(D) Orifice meter

Ans:A

6. For heat transfer across a solid-fluid interface, which one of the following statements is NOT true when the Biot number is very small compared to 1?

(A) Conduction resistance in the solid is very small compared to convection resistance in the fluid
(B) Temperature profile within the solid is nearly uniform
(C) Temperature drop in the fluid is significant
(D) Temperature drop in the solid is significant

Ans

7. In the McCabe-Thiele diagram, if the x -coordinate of the point of intersection of the q -line and the vapor-liquid equilibrium curve is greater than the x -coordinate of the feed point, then the quality of the feed is

(A) super-heated vapor
(B) liquid below bubble point
(C) saturated vapor
(D) saturated liquid

Ans:B

8. For which of the following combinations, does the absorption operation become gas-film controlled?

P. The solubility of gas in the liquid is very high
Q. The solubility of gas in the liquid is very low
R. The liquid-side mass transfer coefficient is much higher than the gas-side mass transfer coefficient
S. The liquid-side mass transfer coefficient is much lower than the gas-side mass transfer coefficient

(A) P & Q
(B) P & R
(C) P & S
(D) Q & R

Ans:B


9. The half-life of an nth order reaction in a batch reactor depends on

(A) only the rate constant
(B) only the rate constant and the order of the reaction
(C) only the rate constant and the initial reactant concentration
(D) the rate constant, initial reactant concentration, and the order of the reaction

Ans

10. In petroleum refining, catalytic reforming is used to convert

(A) Paraffins and naphthenes to aromatics
(B) Paraffins to hydrogen and carbon monoxide
(C) Gas oil to diesel and gasoline
(D) Light olefins to gasoline

Ans:A

11. T he final boiling points of gasoline, diesel, atmospheric gas oil (AGO) and lubricating oils vary as

(A) gasoline > diesel > AGO > lubricating oils
(B) lubricating oils > AGO > diesel > gasoline
(C) AGO > lubricating oils > diesel > gasoline
(D) lubricating oils > diesel > AGO > gasoline

Ans:B

12. The main unit processes used for the production of hydrogen from natural gas are steam reforming (SR), pressure swing adsorption (PSA), low temperature water gas shift reaction (LT WGS) and high temperature water gas shift reaction (HT WGS). The correct sequence of these in the plant is

(A) SR; LT WGS; HT WGS; PSA
(B) PSA; SR; LT WGS; HT WGS
(C) SR; HT WGS; LT WGS; PSA
(D) PSA; HT WGS; LT WGS; SR

Ans:C

13. A thermometer initially at 100°C is dipped at t = 0 into an oil bath, maintained at 150°C. If the recorded temperature is 130°C after 1 minute, then the time constant of thermometer (in min) is

(A) 1.98
(B) 1.35
(C) 1.26
(D) 1.09

Ans

14. The Bode stability criterion is applicable when

(A) Gain and phase curves decrease continuously with frequency
(B) Gain curve increases and phase curve decreases with frequency
(C) Gain curve and phase curve both increase with frequency
(D) Gain curve decreases and phase curve increases with frequency

Ans:A

15. An equimolar mixture of A and B (A being more volatile) is flash distilled continuously at a feed rate of 100 kmol/h, such that the liquid product contains 40 mol % of A. If the relative volatility is 6, then the vapor product, in kmol/h, is

(A) 10
(B) 20
(C) 25
(D) 45

Ans:C