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G-XEC-2012-3

MCQS

Which of the following techniques is NOT used to grow single crystals of semiconductors? (A) Calendering (B) Czochralski (C) Float zone (D) Bridgman

Thermodynamics

A

G-XEC-2012-4

MCQS

Which of the following signals is produced due to the elastic scattering of electrons by a material? (A) Secondary electron (B) Backscattered electron (C) Auger electron (D) Photoelectron

Thermodynamics

B

G-XEC-2012-6

MCQS

Of the following materials, which is the most suitable for an LED emitting at around 380 nm? (A) Direct bandgap material with a small bandgap (B) Indirect bandgap material with a large bandgap (C) Direct bandgap material with a large bandgap (D) Indirect bandgap material with a small bandgap

Thermodynamics

C

G-XEC-2012-7

MCQS

Which material has the lowest specific heat capacity at room temperature? (A) Water (B) Mercury (C) Copper (D) Silver

Thermodynamics

B

G-XEC-2013-15

NUM

The band gap of a semiconducting material used to make an LED is 1.43 eV. What will be the minimum wavelength ofthe radiation emitted by this LED, in μm?

Thermodynamics

0.85 to 0.89

G-XEC-2014-3

MCQS

At room temperature, the typical barrier potential for silicon p-n junction in Volt (V) is (A) 0.7 * $10^(-23)$ (B) 0.07 (C) 0.70 (D) 7.0

Thermodynamics

C

G-XEC-2014-6

MCQS

At low injection level, a forward biased p-n junction would have (A) no charge carriers (B) minority carrier concentration much more than majority carrier concentration (C) minority carrier concentration equal to majority carrier concentration (D) minority carrier concentration much less than majority carrier concentration

Thermodynamics

D

G-XEC-2014-12

NUM

A copper cup weighing 140 g contains 80 g of water at 4 °C. Specific heats of water and copper are 4.18 and 0.385 J/g °C, respectively. If 100 g of water that is at 90 °C is added to the cup, the final temperature of water in °C is

Thermodynamics

48 to 49

G-XEC-2014-17

MCQS-NUM

The energy in eV and the wavelength in μm, respectively, of the photon emitted when an electron in a hydrogen atom falls from n = 4 to n = 2 state is (A) 3.0, 0.413 (B) 2.55, 0.365 (C) 2.75, 0.451 (D) 2.55, 0.487

Thermodynamics

D

G-XEC-2015-44-1

MCQS

Arrange the following elements in order of increasing melting point: (P) gallium (Q) tungsten (R) aluminium (S) gold Options: (A) P < R< Q < S (B) S < P < R < Q (C) P < R < S < Q (D) R < S < Q < P

Thermodynamics

C

G-XEC-2015-45-2

MCQS

When the atoms in a solid are separated by their equilibrium distance, (A) the potential energy of the solid is lowest (B) the force of attraction between the atoms is maximum (C) the force of repulsion between the atoms is zero (D) the potential energy of the solid is zero

Thermodynamics

A

G-XEC-2015-47-4

MCQS

Which of the following statements is TRUE about the glass transition temperature (Tg)? (A) Tg appears below the melting temperature in a perfectly crystalline material (B) Upon heating through Tg, heat capacity remains constant but the thermal expansion coefficient changes (C) Upon heating through Tg, heat capacity changes but the thermal expansion coefficient remains the same (D) Upon heating through Tg, both the heat capacity and thermal expansion coefficient change

Thermodynamics

D

G-XEC-2015-48-5

MCQS

The slope of a graph of $log_e$(conductivity) versus 1/T (where T is the temperature) for an intrinsic semiconductor with energy gap $E_g$, is (A) $E_g$/2k (B) –$E_g$/2k (C) $E_g$/k (D) −$E_g$/k

Thermodynamics

B

G-XEC-2015-55-12

NUM

With increasing temperature from 15°C in winter to 45°C in summer, the length of an iron rail track increases by 0.05 cm. Calculate the original length of the iron rail track in cm. (linear thermal expansion coefficient of iron is 11.0 * $10^(-6)$ $K^(-1)$)

Thermodynamics

151 to 152

G-XEC-2015-65-22

NUM

What would be the maximum number of electron-hole pairs that can be generated using a silicon detector irradiated by x-ray of energy 1.54 keV. The band gap of silicon is 1.1 eV.

Thermodynamics

1399 to 1401

G-XEC-2016-3

MCQS

Which of the following thermodynamic properties shows a discontinuity during a second-order phase transition? (A) Volume (B) Enthalpy (C) Entropy (D) Heat capacity

Thermodynamics

D

G-XEC-2016-5

MCQS

For a typical metal at room temperature and atmospheric pressure, the Fermi energy is defined as the energy level for which the probability of occupancy is: (A) 0 (B) 0.25 (C) 0.5 (D) 1

Thermodynamics

C

G-XEC-2016-13

NUM

Given: Planck’s constant, h = 6.626 * $10^(−34)$ J s, the charge of an electron, e = 1.6 * $10^(−19)$ C, and speed of light, c = 3 * $10^8$ m $s^(−1)$. A direct bandgap semiconductor has a bandgap of 1.8 eV. The threshold value of the wavelength(in Å) BELOW which this material will absorb radiation is

Thermodynamics

6850 : 6950

G-XEC-2016-21

MCQS

In the photoelectric effect, electrons are ejected (A) at all wavelengths, as long as the intensity of the incident radiation is above a threshold value. (B) at all wavelengths, as long as the intensity of the incident radiation is below a threshold value. (C) at all intensities, as long as the wavelength of the incident radiation is below a threshold value. (D) at all intensities, as long as the wavelength of the incident radiation is above a threshold value

Thermodynamics

C

G-XEC-2018-4

MCQS

An electron makes a transition from the valence band to the conduction band in an indirect band gap semiconductor. Which one of the following is true? (A) Energy of the electron decreases. (B) A photon is emitted in the process. (C) A phonon is annihilated in the process. (D) A photon is created in the process.

Thermodynamics

C

G-XEC-2018-18

NUM

When 3 identical non-interacting spin ½ particles are put in an infinite potential well, the ground state energy of the system is 18 meV. If instead, seven particles are put inside the potential well, the new ground state energy in meV is?

Thermodynamics

132 to 132

G-XEC-2018-22

NUM

Given: Activation energy Q = 148 kJ $mol^(-1)$, Gas constant, R = 8.314 J $mol^(-1)$ $K^(-1)$. Mild steel is carburized at 1300 K for 1 hour to obtain a certain case depth. Keeping the time as 1 hour, the case depth can be doubled by increasing the temperature to what temperature(in K)? (round off to the nearest whole number)

Thermodynamics

1420 to 1480

G-XEC-2019-7

MCQS

GaAs has advantage over silicon when used in intergrated circuits at low power because it has (A) larger band gap (B) more than one element (C) higher electron mobility (D) higher hole mobility

Thermodynamics

C

G-XEC-2019-9

MCQS-NUM

(Given: energy gap of Ge = 0.67 eV, Planck’s constant h = 6.63 * $10^(-34)$ J s, velocity of light c = 3 * $10^(8)ms^(-1)$ and 1 eV = 1.6*$10^(-19)$ J ). The maximum wavelength of radiation to which Germanium (Ge) is opaque will be (A) 0.8 μm (B) 1.8 μm (C) 2.8 μm (D) 4.8 μm

Thermodynamics

B

G-XEC-2019-15

NUM

(Given: Constants A = 6* $10^(-20)$ J $nm^3$, B = 2.1 * $10^(-22)$ J $nm^(7)$). The potential energy, U(r), of a pair of atoms spaced at a distance r in a solid is given by U(𝑟)= −(𝐴/$𝑟^3$) + (𝐵/$𝑟^7$) . The equilibrium distance(in nm) between the atom pair is? (round off to 2 decimal places)

Thermodynamics

0.28 to 0.32

G-XEC-2019-18

NUM

(Given: Planck’s constant h = 6.63 * $10^(-34)$ J s, 1ev = 1.6*$10^(-19)$ J, electron mass = 9.11×$10^(-31)$ kg ). The zero point energy(in ev) of an electron in a box of 0.2 nm width is? (round off to 1 decimal place)

Thermodynamics

9.2 to 9.6

G-XEC-2020-8

NUM

A ceramic material is periodically heated and cooled between 25° C and a higher temperature $T_f$. During thermal cycling, the material remains dimensionally constrained. The material can withstand a maximum compressive stress of 200 MPa without failure. Material's coefficient of thermal expansion is 7.5* $10^(-6)°C^(-1)$ and modulus of elasticity (E) is 200GPa. The lowest value of $T_f$( in °C) at which material will fail is?(round off to the nearest integer.). Assume that there is no plastic deformation during thermal cycling.

Thermodynamics

157 to 159

G-XEC-2020-9

NUM

Given that $γ_(sl)$ (solid liquid interfacial energy) is 0.18 $J.m^(-2)$ and $ΔG_v$ (change in volume free energy upon transformation from liquid to solid) is $T_s$ is 0.18*$10^(9)J.m^(-3)$. During homogeneous solidification of a liquid metal, the radius of critical nucleus(in nanometer, nm) at a temperature $T_s$ which is below the melting point($T_m$), is ? (round-off to one decimal place).

Thermodynamics

1.9 to 2.1

G-XEC-2021-7

MCQS

Which of the following deposition conditions favour the formation of larger grains in thin film? (A) Low deposition rate and low substrate temperature (B) Low deposition rate and high substrate temperature (C) High deposition rate and low substrate temperature (D) High deposition rate and high substrate temperature

Thermodynamics

B

G-XEC-2021-8

MCQS

A metal has a melting point of 600 °C. By rapid cooling, liquid metal can be made to solidify either at 500 °C or 400 °C or 300 °C. Critical size of the solid nuclei is (A) same for solidification at 400 °C and 500 °C (B) smaller for solidification at 400 °C as compared to solidification at 500 °C (C) larger for solidification at 400 °C as compared to solidification at 500 °C (D) the smallest for solidification at 300 °C

Thermodynamics

B; D

G-XEC-2022-11

MCQS

For a glass marginally below its glass transition temperature, which one of the following statements is true? (A) Glass has higher enthalpy than both the corresponding crystalline and liquid phases (B) Glass has lower enthalpy than both the corresponding crystalline and liquid phases (C) Glass has higher entropy than the corresponding crystalline phase and lower entropy than the corresponding liquid phase (D) Glass has lower entropy than the corresponding crystalline phase and higher entropy than the corresponding liquid phase

Thermodynamics

C

G-XEC-2015-56-13

NUM

What is the thickness (in µm) of a germanium crystal layer that would be required for absorbing 80% of the incident radiation whose wavelength is 1.3 µm? The absorption coefficient (α) of germanium at 1.3 µm is 3.3 * $10^5$ $m^(-1)$.

Thermodynamics

4.8 to 4.9

G-XEC-2016-17

NUM

A batch of spherical titania nanoparticles, uniform in size, has a specific surface area of 125 $m^2$ $^(g−1)$. If the density of titania is 4.23 g $cm^(−3)$, the diameter(in nm) of the particles is

Thermodynamics

11.30 : 11.40

G-XEC-2018-16

NUM

(Given: Planck’s constant, h = 6.6 * $10^(-34)$ J s; speed of light, c = 3 * $10^8$ m $s^(-1)$). The atoms in a gas laser have two energy levels such that a transition from the higher to the lower level releases a photon of wavelength 500 nm. If 7 * $10^(20)$ atoms are pumped into the upper level with 4 * $10^(20)$ atoms in the lower level, the amount of energy released in a single pulse in Joules (give answer up to 2 decimal places).

Thermodynamics

59.00 to 60.00

G-XEC-2018-17

NUM

(Given: Planck’s constant, h = 6.6 * $10^(-34)$ J s; mass of electron = 9.1 * $10^(31)$ kg). The speed of an electron is measured to be 300 m $s^(-1)$ with an uncertainty of 0.01%. The fundamental accuracy with which the position of the electron can be determined simultaneously with the speed in the same experiment in mm? (give answer up to 2 decimal places)

Thermodynamics

1.85 to 2.00

G-XEC-2019-19

NUM

(Given: Planck’s constant h = 6.63 * $10^(-34)$ J s, electron charge = 1.6*$10^(-19)$ C, electron rest mass = 9.11×$10^(-31)$ kg ). The de Broglie wavelength of an electron accelerated across a 300 kV potential in an electron microscope is x * $10^(-12)$ m. Find x. Ignore relativistic effects. (round off to 2 decimal places)

Thermodynamics

2.10 to 2.35

G-XEC-2019-20

NUM

A stress of 17 MPa is applied to a polymer serving as a fastener in a complex assembly. At constant strain the stress drops to 16.6 MPa after 100 hours. The stress on the polymer must remain above 14.5 MPa in order for the assembly to function properly. The expected life(in hours) of the assembly is? (round off to the nearest integer)

Thermodynamics

666 to 670

G-XEC-2020-13

MCQS-NUM

Given: Activation energy for the formation of schottky defect = 250 kJ $mol^(-1)$. Avogadro number = 6.023* $10^(23)mol^(-1)$, Universal Gas Constant = 8.314 $J.K^(-1).mol^(-1)$. The number of Schottky defects per mole of KCL at 300 °C under equilibrium condition will be: (A) 1.21 * $10^(18)$ (B) 1.52 * $10^(16)$ (C) 9.75 (D) 2.42 * $10^(12)$

Thermodynamics

D

G-XEC-2020-16

NUM

Intrinsic carrier concentration of Si, $n_i$ is gives as: $n_i$ = 2* $([2πmk_(B)T]/h^(2))^(3/2)$ * $exp(-{E_g/k_(B)T})$ wher Mass of an electron, m = 9.1 * $10^(-31)$ kg, charge of an electron, e = 1.6 * $10^(-19)$ C, Boltzmann constant $k_B$ = 1.38 * $10^(-23)$ J.$K^(-1)$, Planck’s constant h = 6.6 * $10^(-34)$ J.$s^(-1)$. Pure silicon (Si) has a band gap ($E_g$) of 1.1 eV. This Si is doped with 1 ppm (parts per million) of phosphorus atoms. Si contains 5 * $10^(28)$ per atoms per $m^3$ in pure form. At temperature T = 300K, the shift in Fermi energy(in ev) upon doping with respect to intrinsic Fermi level of pure Si will be? (with appropriate sign and round-off to two decimal places).

Thermodynamics

0.33 to 0.45

G-XEC-2020-21

NUM

Isothermal weight gain per unit area (ΔW/A, where ΔW is the weight gain(in mg) and A is the area (in $cm^2$)) during oxidation of a metal at 600°C follows parabolic rate law, where ΔW/A = 1.0 mg.A$cm^(-2)$ after 100 min of oxidation. The ΔW/A (in mg.$cm^(-2)$) after 500 min at 600°C will be? (round-off to two decimal places).

Thermodynamics

2.20 to 2.28

G-XEC-2021-20

NUM

At 1000 K, the linear thermal expansion coefficients of graphite, parallel and perpendicular to the graphite layers, are 0.8 * $10^(−6)K^(−1)$ and 29 * $10^(−6)K^(−1)$, respectively. The percentage increase in the volume of graphite when heated from 900 K to 1100 K is? (round off to 2 decimal places)

Thermodynamics

0.60 to 0.62

G-XEC-2022-15

MCQS

A student aims to deposit a thin metallic film on $SiO_2$ substrate, with an adhesion layer between the metal film and substrate, in a contiguous planar fashion. Island type of growth must be avoided. The student performs an extensive optimization exercise. Which one of the following steps is in the right direction? (A) Choose a metallic adhesion layer with very low interfacial energy with the deposited thin film (B) Choose a metallic adhesion layer with very low interfacial energy with $SiO_2$, irrespective of its interaction with metal film to be deposited (C) Increase the substrate temperature and decrease the deposition rate (D) Use intermittent stages of deposition followed by annealing

Thermodynamics

A

G-XEC-2022-20

NUM

Given: $𝑁_A$: Avogadro’s number = 6.02 * $10^(23)mole^(-1)$, $𝑘_B$: Boltzmann’s constant = 8.62 * $10^(-5)$ eV/K, 𝑇: Absolute temperature, Mobility of electrons in the semiconductor = 0.14 $m^2$/(V s), Mobility of holes in the semiconductor = 0.06 $m^2$/(V s), Absolute charge of an electron = 1.60 * $10^(-19) C. The resistivity of a pure semiconductor at 298 K is 3000 Ωm. Assume that the number of electrons excited ($𝑛_e$) across the band gap is given by the relation $n_e$ = $(N_A)*exp(-{E_g/k_(B)T})$. The band gap(in ev) ($𝐸_g$) of the semiconductor is? (Round off to two decimals)

Thermodynamics

0.45 to 0.47

G-XEC-2022-21

NUM

A new glass material is developed to minimize the transmission of the light through the window with glass panel of thickness 5 mm. The refractive index of the glass material is 1.5 and the absorption coefficient can be changed from 0.3 $cm^(-1)$ to 1 $cm^(-1)$. In the given range of absorption coefficients, the ratio of the maximum to the minimum fraction of the light coming out of the other side of the glass panel is? (Round off to two decimal places)

Thermodynamics

1.40 to 1.43

G-META-12-14

MCQS

During the solidification of a pure metal, it was found that dendrites are formed. Assuming that the liquid-solid interface is at the melting temperature, the temperature from the interface into the liquid (A) Decreases (B) Increases (C) Remains constant (D) Increases and then decreases

Thermodynamics

A

G-META-12-18

MCQS

At equilibrium spacing in a crystalline solid, which of the following is true for net inter-atomic force (F) and potential energy (U) (A) F is zero and U is zero (B) F is zero and U is minimum (C) F is minimum and U is zero (D) F is minimum and U is minimum

Thermodynamics

B

G-META-12-19

MCQS

The property of a material that CANNOT be significantly changed by heat treatment is (A) Yield strength (B) Ultimate tensile strength (C) Ductility (D) Elastic modulus

Thermodynamics

D

G-META-12-33

MCQS-NUM

Consider a reaction with activation energy of 8.314 kJ/mol that takes place at 300 K. If the reaction rate is to be tripled, the temperature of the reaction should be (A) 174.5 K (B) 447.5 K (C) 600.5 K (D) 847.5 K

Thermodynamics

B

G-META-12-35

MCQS-NUM

The reduction of FeO with CO gas in co-current flow is given by the following equation: FeO + CO = Fe + $CO_2$ ∆G°= 8120 J at 1173K. The ratio of $p_(CO)/p_(CO_2)$ for this reaction at 1173 K is (A) 0.0 (B) 0.25 (C) 0.44 (D) 2.3

Thermodynamics

D

G-META-13-3

MCQS

In a binary system A-B, $ε_(AA)$, $ε_(BB)$ and $ε_(AB)$ correspond to A-A, B-B and A-B bond energies respectively. The miscibility gap will occur if (A) $ε_(AB)$ > ½ ($ε_(AA)$ + $ε_(BB)$) (B) $ε_(AB)$ < ½ ($ε_(AA)$ + $ε_(BB)$) (C) $ε_(AB)$ = ½ ($ε_(AA)$ + $ε_(BB)$) (D) $ε_(AB)$ < ¼ ($ε_(AA)$ + $ε_(BB)$)

Thermodynamics

A

G-META-13-12

MCQS

Isothermal compressibility of a material is given by (A) -1/p* (∂V/∂p)$_T$ (B) 1/p* (∂V/∂p)$_T$ (C) -1/V * (∂V/∂p)$_T$ (D) 1/V * (∂V/∂p)$_T$

Thermodynamics

C

G-META-13-23

NUM

The total number of possible heat transfer mode(s) is?

Thermodynamics

3

G-META-13-50

MCQS-NUM

Integral enthalpy of mixing (in J/mol) of liquid (Cu, Zn) solution can be approximated by mix $ΔH^(mix)$ = -19250 * $χ_(Cu)$ * $χ_(Zn)$. The corresponding partial molar enthalpy of mixing (in J/mol) for Cu is (A) 19250 * $(χ_(Zn))^2 (B) -19250 * $(χ_(Cu))^2 (C) 38500*$χ_(Zn)$ -19250 * $(χ_(Zn))^2 - 19250 (D) -19250 * $(χ_(Zn))^2

Thermodynamics

D

G-META-13-51

MCQS-NUM

Integral enthalpy of mixing (in J/mol) of liquid (Cu, Zn) solution can be approximated by mix $ΔH^(mix)$ = -19250 * $χ_(Cu)$ * $χ_(Zn)$. Assuming regular solution behaviour, the solution parameter (in J/mol) is (A) -19250 (B) -9625 (C) 13.75 (D) 2315.4

Thermodynamics

A

G-META-14-8

MCQS

The Pilling-Bedworth ratio is defined as (A) the molar weight of an oxide divided by the molar weight of the metal consumed in oxide formation. (B) the volume of the oxide divided by the volume of the metal consumed in oxide formation. (C) the density of the oxide divided by the density of the metal consumed in oxide formation. (D) the molar Gibbs energy of the oxide divided by the Gibbs energy of the metal consumed in oxide formation.

Thermodynamics

B

G-META-14-29

NUM

The activity coefficient of Q in a liquid Q-R alloy is represented by the following equation at a given temperature. ln $𝛾_𝑄$ = $0.6*(𝑥_R)^2$ - 0.2*$(𝑥_R)^3$. What is the activity of Q in an alloy of composition 𝑥_𝑅 = 0.6 at the same temperature?

Thermodynamics

0.46 TO 0.49

G-META-14-33

NUM

What is the theoretical requirement of air (in $m^ 3$ at STP) for the complete combustion of 100 $m^3$ (at STP) of a fuel consisting of pure $CH_4$? Assume that air contains 21 vol.% of oxygen.

Thermodynamics

951 TO 953

G-META-15-5

MCQS

In an Ellingham diagram, the standard free energy change ∆𝐺° for the oxidation reaction of a metal M given by: 𝑥𝑀(𝑠𝑠) + $𝑂_2$(𝑔) → $𝑀_(𝑥)𝑂_2$(𝑠) , is plotted as a function of temperature. The slope of this line is positive because (A) ∆S° is positive (B) ∆S° is negative (C) ∆H° is positive (D) ∆H° is negative

Thermodynamics

B

G-META-15-16

MCQS

When boron (trivalent) is doped to silicon, the resulting material is (A) a p-type semiconductor. (B) an n-type semiconductor. (C) a superconductor. (D) an insulator

Thermodynamics

A

G-META-15-31

MCQS

C (s) + $CO_2$ (g) ⇋ 2CO (g) is an important reaction in iron making. Given $∆𝐻°_(298)$ = 172000 joules per mole of $CO_2$, which of the following conditions will favour the forward reaction? (A) Increasing both temperature and pressure. (B) Decreasing temperature and increasing pressure. (C) Decreasing both temperature and pressure. (D) Increasing temperature and decreasing pressure.

Thermodynamics

D

G-META-15-38

NUM

Configurational entropy due to ideal mixing in a binary A-B system is expressed as: $∆S_(mix)$ = -R*( $X_(A)*ln[X_(A)]$ + $X_(B)ln[X_(B)]$) where $X_A$ and $X_B$ are mole fractions of A and B respectively. $∆𝑆_(mix)$ is maximum at what $X_A$?

Thermodynamics

0.5

G-META-16-4

MCQS

The first law of thermodynamics can be stated as [where, E, Q and W denote internal energy, heat and work, respectively] (A) dE = δQ – δW (B) dQ = dE – δW (C) δW = dQ + dE (D) dW = δQ – δE

Thermodynamics

A

G-META-16-6

MCQS

Activation energy of a chemical reaction, homogeneous or heterogeneous, is graphically estimated from a plot between (A) k versus T (B) 1/k versus T (C) 1/k versus ln T (D) ln k versus 1/T

Thermodynamics

D

G-META-16-42

MCQS

Zinc oxide is reduced at a constant temperature in a closed reactor using ZnO(s) and C(s) as the only starting materials. The following reactions are assumed to be at thermodynamic equilibrium: ZnO(s) + C(s) = Zn(g) + CO(g) and 2CO(g) = $CO_2$(g) + C(s). Assume ideal gas behaviour. Based on mole balance, the relationship applicable to the system at equilibrium is (A) $p_(Zn)$ = $p_(CO)$ + $2*p_(CO_2)$ (B) $p_(Zn)$ = 2*$p_(CO)$ + $p_(CO_2)$ (C) $p_(Zn)$ = $p_(CO)$ + $p_(CO_2)$ (D) $p_(Zn)$ = 0.5*$p_(CO)$ + $2*p_(CO_2)$

Thermodynamics

A

G-META-16-54

MCQS-NUM

A liquid phase sintered SiC-Ni composite has a solid-solid grain boundary energy ($γ_(SiC-SiC)$) of 0.80 $J.m^(-2)$ and a solid-liquid ($γ_(SiC-Ni)$) interfacial energy of 0.45 $J.m^(-2)$. For a SiC grain size of 20 µm, the average interparticle (SiC-SiC) neck size (in µm) is: (A) 3.03 (B) 4.28 (C) 9.16 (D) 18.32

Thermodynamics

C

G-META-17-35

NUM

$CaCO_3$(s) dissociates in a closed system according to the reaction: $CaCO_3$(s) = CaO(s) + $CO_2$(g) Assuming the reaction is in thermodynamic equilibrium, the degree(s) of freedom F is?

Thermodynamics

1

G-META-17-38

NUM

Given: $ΔH°_(298)$ (CO → $CO_2$) = -282000 kJ.(kg-mol $CO)^(-1)$, $C_p(CO_2)$ = 44kJ.(kg-mol $K)^(-1)$. A stoichiometric mixture of CO and pure oxygen at 1 atm and 25°C flows into a combustion reactor. The molar flow rate of CO entering the reactor is $1kg-mol.h^(-1)$. The adiabatic flame temperature(in K) for the combustion of CO with stoichiometric oxygen is?(answer up to two decimal places)

Thermodynamics

6650.00 TO 6750.00

G-META-17-42

NUM

Given: Entropy change associated with heating orthorhombic sulfure from 0K to 368.5 K is 36.86 $J.K^(-1)$. Entropy change asssociated with cooling monoclinic sulfur from 368.5K to 0 K is -37.8 $J.K^(-1)$. Pure orthorhombic sulfure transforms to stable monoclinic sulfure monoclinic sulfure above 368.5K. Applying Third law of thermodynamics, the value of entropy (in $J.K^(-1)$) of transformation of 368.5 K is ?(answer up to two decimal places)

Thermodynamics

0.92 TO 0.96

G-META-17-43

NUM

Given: surface energy γ = 0.177 $J.m^(-2)$; change in volume free energy $ΔG_v$ = -2.8 * $10^8$ $J.m^(-3)$. For homogenous nucleation of solid in a liquid of a pure metal, the critical edge length(in nm) of a cube shaped nucleus is?(answer up to two decimal places)

Thermodynamics

2.50 TO 2.60

G-META-17-55

MCQS-NUM

Given: Melting points of tungsten and nickel are 3410°C and 1453°C, respectively. W-Ni compact is prepared by liquid phase sintering at 1500° C. If the size of tungsten grains is 40 µm and the interfacial tungsten -tungsten and tungsten- nickel energies are 0.52 and 0.30 $J.m^(-2)$ respectively, the predicted avergae neck size (in µm) of sintered tungsten grain is: (A) 10 (B) 15 (C) 20 (D) 25

Thermodynamics

C

G-META-18-2

MCQS

What is the most abundant anion in a $2CaO.SiO_2$ melt? (A) $(SiO_4)^(-4)$ (B) $(Si_(2)O_(7))^(-6)$ (C) $(Si_(3)O_(10))^(-8)$ (D) $(Si_(4)O_(14))^(-10)$

Thermodynamics

A

G-META-18-11

MCQS

At equilibrium, the maximum number of phases in a three-component system at CONSTANT PRESSURE is: (A) 1 (B) 2 (C) 3 (D) 4

Thermodynamics

D

G-META-18-26

MCQS-NUM

Given: Gas constant R = 8.314 J $K^(-1)mol^(-1)$. The molar free energy (J $mol^(-1)$) of a liquid solution of a binary A-B alloy as a function of temperature ( T ) and composition (x, the mole fraction of B) is given by: $G^(L)(T,x)$ = (1-x)*$[G_(A)]^(0,L)$ + x*$[G_(B)]^(0,L)$ + RT[xlnx + (1-x)ln(1-x)] + 4000x(1-x) where $(G_(A))^(0,L)$ and $(G_(B))^(0,L)$ are the molar free energies of pure liquid A and pure liquid B. What is the excess molar free energy, $𝐺^(XS,L)$, for an alloy with 𝑥 = 0.5 at 𝑇 = 1000 K? (A) 1000 J $mol^(-1)$ (B) - 2000 J $mol^(-1)$ (C) 4763 J $mol^(-1)$ (D) - 5763 J $mol^(-1)$

Thermodynamics

A

G-META-18-39

MCQS-NUM

If the solid-liquid interfacial energy increases by 10%, the energy barrier for homogeneous nucleation of a spherical solid from the liquid, will change by: (A) 21% (B) 33% (C) -10% (D) 46%

Thermodynamics

B

G-META-18-49

NUM

Given: The enthalpy of fusion for the metal is 4000 kJ $kg^(-1)$ ; The gas-droplet convective heat transfer coefficient is 200 W $m^(-2)K^(-1)$. ; Density of liquid metal is 2700 kg $m^(-3)$. A spherical liquid metal droplet of diameter 1 mm is solidified in a stream of gas at 300 K. Assuming that the metal droplet remains at its melting point of 900 K and neglecting radiative losses, the time(in seconds to one decimal place) to complete the solidification is?

Thermodynamics

14.9 TO 15.1

G-META-18-50

NUM

At a temperature of 710 K, the vapour pressure of pure liquid Zn is given by: $𝑝_(𝑍𝑛)(𝑋_(𝑧𝑛)$ = 1.0) = 3.6 * $10^(−4)$ atm. The Raoultian activity coefficient ($𝛾_(𝑍𝑛)$) of Zn in Zn-Cd alloy liquid at 710 K is approximated by: ln($𝛾_(𝑍𝑛)$) = 0.875 * $(1 − $𝑋_(𝑍𝑛)$)^2$. The ratio [$𝑝_(𝑍𝑛)(𝑋_(𝑧𝑛)=0.7)/𝑝_(𝑍𝑛)(𝑋_(𝑧𝑛)=1.0)$] for a liquid alloy with $𝑋_(𝑧𝑛)$ = 0.7 is?(upto two decimal places)

Thermodynamics

0.74 TO 0.78

G-META-19-12

MCQS

The Boudouard (or, carbon gasification) reaction is (A) C(s) + (1/2)$O_2$(g) → CO(g) (B) C(s) + $O_2$(g) → $CO_2$(g) (C) C(s) + $CO_2$(g) → 2CO(g) (D) CO(g) + (1/2)$O_2$(g) → $CO_2$(g)

Thermodynamics

C

G-META-19-40

NUM

Given: Vapour pressure of pure zinc $(p_(zn))°$ at 900K is 0.027 atm. Henry's law coefficient $(γ_(zb))°$ for zinc at infinite dilution solution in lead on Raoultian scale is 8.55. 1 torr = 1.316 * $10^(-3)$ atm. The partial pressure of zinc(in torr, rounded off two decimal places) in equlibrium with liquid lead containing 0.03 mole % zinc at 900K is?

Thermodynamics

0.04 TO 0.06

G-META-19-47

NUM

Given: Shear modulus of iron = 82 GPa, Burger’s vector, b = a/2[1 1 1], a = 0.2856 nm. Cold working of iron leads to increase in dislocation density from $10^(10)$ to $10^(15)𝑚^(−2)$ . The associated stored energy (in 𝑴𝑱. $𝒎^(−𝟑)$, rounded off to one decimal place) is

Thermodynamics

0.4 TO 5.1

G-META-20-10

MCQS

When 1 mole of $C_(3)H_(8)$ at 300K is burnt with stoichiometric amount of oxygen at 300K to form $CO_2$ and $H_(2)O$, the adiabatic flame temperature is 5975K. If $C_(3)H_(8)$ is burnt under the same conditions but with excess oxygen, the adiabatic flame temperature will be: (A) Equal to 5975K irrespective of the amount of excess oxygen (B) higher than 5975K irrespective of the amount of excess oxygen. (C) lower than 5975 K irrespective of the amount of excess oxygen. (D) higher or lower than 5975K depending on the amount of excess oxygen

Thermodynamics

C

G-META-20-11

MCQS-NUM

Two solid spheres X and Y of identical diameter are made of different materials having thermal diffusivities 100*$10^(-6)m^(2)s^(-1)$ and 25*$10^(-6)m^(2)s^(-1)$ respectively. Both spheres are heated in a furnace maintained at 1000K. If the center of the sphere X reaches 800K in 1 hour, time required for the center of sphere Y to reach 800K is (A) 1 hour (B) 2 hours. (C) 4 hours. (D) 16 hours.

Thermodynamics

C

G-META-20-36

MCQS-NUM

Given, atomic weight of Sn is 118.7 and Mg is 24.3. The Mg-Sn phase diagram exhibits two eutectics on either side of the high melting intermetallic line compound, $Mg_2Sn$, as given below. At 561° C: L(36.9 wt.% Sn) → α(14.48 wt.% Sn) + $Mg_2Sn$. At 203° C: L (97.87 wt.% Sn) → β-Sn (almost 100 wt.% Sn) + $Mg_2Sn$ After the eutectic reaction has gone to completion and equilibrium has been attained at a temperature just below 561° C, the amount(in wt.%) of eutectic constituent present in the alloy, Mg-50 wt.% Sn, is approximately? (A) 25 (B) 38 (C) 62 (D) 75

Thermodynamics

C

G-META-20-37

MCQS

Determine the correctness or otherwise of the following Assertion [a] and the Reason [r]. Assertion[a]: Low alloy steels used for medium-temperature creep resistance often have additions of strong carbide-forming elements. Reason[r]: During creep deformation, the particles with higher misfit with the matrix, lose coherency. (A) Both [a] and [r] are true and [r] is the correct reason for [a]. (B) Both [a] and [r] are true but [r] is not the correct reason for [a]. (C) Both [a] and [r] are false. (D) [a] is true but [r] is false.

Thermodynamics

B

G-META-21-6

MCQS

Given: ($ΔH_(mix)$ - Mixing enthalpy, $a_B$ - activity of B and $X_B$ - Mole fraction of B). Elements A and B have the same crystal structure. For a dilute solution of B in A, which one of the following is true? (A) If $ΔH_(mix)$ = 0, then $a_B$ < $X_B$ (B) If $ΔH_(mix)$ = 0, then $a_B$ > $X_B$ (C) If $ΔH_(mix)$ > 0, then $a_B$ < $X_B$ (D) If $ΔH_(mix)$ < 0, then $a_B$ < $X_B$

Thermodynamics

D

G-META-21-11

MCQS

For a zeroth order chemical reaction, which one of the following is FALSE? (A) Concentration versus time plot is a straight line. (B) Increase in concentration of reacting species increases the rate of reaction (C) Half-life depends on the initial concentration and zero-order rate constant. (D) Rate of reaction depends on temperature

Thermodynamics

B

G-META-21-19

NUM

Consider homogenous nucleation of a spherical solid in liquid. For a given undercooling, if surface energy of a nucleus increases by 20%, the corresponding increase(in percent) in the critical radius of the nucleus is?(round off to nearest integer)

Thermodynamics

20

G-META-21-29

MCQS

Number of degrees of freedom for the following reacting system is: M(s) + $CO_2$(g) = MO(s) + CO(g) (A) 0 (B) 1 (C) 2 (D) 3

Thermodynamics

C

G-META-21-30

MCQS

Given: $ΔH_(mix)^(solid)$ - Enthalpy of mixing of solid, $ΔH_(mix)^(liquid)$- Enthalpy of mixing of liquid. The condition for getting the binary phase diagram of A-B (shown below) is: (A) $ΔH_(mix)^(solid)$ = 0 and $ΔH_(mix)^(liquid)$ = 0 (B) $ΔH_(mix)^(solid)$ << 0 and $ΔH_(mix)^(liquid)$ = 0 (C) $ΔH_(mix)^(solid)$ > 0 and $ΔH_(mix)^(liquid)$ = 0 (D) $ΔH_(mix)^(solid)$ = 0 and $ΔH_(mix)^(liquid)$ << 0

Thermodynamics

B

G-META-21-54

NUM

Assume: Weight gain is proportional to square root of time. Nickel undergoes isothermal oxidation at 800K for a duration of 400s resulting in a weight gain of 2mg $cm^(2)$. The weight gain (mg $cm^2$) after a duration of 1600s is?(round off to nearest integer).

Thermodynamics

4

G-META-22-12

MCQS

Given: Equilibrium partial pressure of $N_2$ (gas) is $𝑝_(N_2)$. According to Sieverts’ law, the equilibrium solubility of $N_2$ (gas) in molten steel is proportional to? (A) $𝑝_(N_2)$ (B) $[𝑝_(N_2)]^(1/2)$ (C) 1/$𝑝_(N_2)$ (D) $[𝑝_(N_2)]^(2)$

Thermodynamics

B

G-META-22-43

MCQS

Which of the following statement(s) is(are) TRUE about black body radiation? (A) Among all radiation emitted by an ideal black body at room temperature, the most intense radiation falls in the visible light spectrum (B) The total emissive power of an ideal black body is proportional to the square of its absolute temperature (C) The emissive power of an ideal black body peaks at a wavelength λ which is inversely proportional to its absolute temperature (D) The radiant energy emitted by an ideal black body is greater than that emitted by the non-black body at all temperatures above 0 K

Thermodynamics

C,D

G-META-13-2

MCQS

As the concentration of point defects in a crystal increases, its configurational entropy (A) does not change (B) decreases (C) increases (D) initially increases and then decreases

Thermodynamics

D

G-META-13-4

MCQS

Critical value of the Gibbs energy of nucleation at equilibrium temperature is (A) zero (B) infinite (C) positive (D) negative

Thermodynamics

B

G-META-14-53

NUM

The specific heat ($C_p$) of pure iron expressed in J/(mol.K) as a function of temperature T (in K) is given as: $C_p$ = 17.49 + 24.77 * $10^(-3)*T$. What is the change in the enthalpy of pure iron (in J/mol) when it is heated from 25°C to 700°C?

Thermodynamics

22380 TO 22480

G-META-15-32

NUM

Consider the reaction: $Fe_(3)O_(4) (solid, pure) + CO (gas, 1 atm) →3FeO (solid, pure) + $CO_2$ (gas, 1 atm). For this reaction, $∆𝐺°_(1200)$ = −8000 joules per mole of CO and R = 8.314 J $mol^(-1)K^(-1). The equilibrium ratio, $𝑝_(C0_2)$/ $𝑝_(CO)$ for the reaction at 1200 K and 1 atm is ?

Thermodynamics

2.1 TO 2.3

G-META-15-39

NUM

Melting point of a metal is 1356 K. When the liquid metal is undercooled to 1256 K, the free energy change for solidification, $∆G^(L→S)$ = −1000 J $mol^(-1)$. On the other hand, if the liquid metal is undercooled to 1200 K, the free energy change (in J $mol^(-1)$) for solidification is ?

Thermodynamics

-1600 TO -1500

G-META-15-47

NUM

Assume that both solid and liquid remain at the melting point while they are in the mould. At the mould exit of a continuous caster, the metal consisting of a solidified shell with a liquid metal core exits at the rate of 35 kg $s^(-1)$. Given that the latent heat of fusion is 3 × $10^(5) J $kg^(-1)$ and the total rate of heat removal by the mould is 4.2 × $10^6$ W, the mass fraction of solid at the mould exit is?

Thermodynamics

0.39 TO 0.41

G-META-16-32

NUM

The change of standard state from pure liquid to 1 wt.% for Si dissolved in liquid Fe at 1873 K is expressed as Si (liq.) = Si (1 wt.%). Given that the activity coefficient of Si at infinite dilution in Fe is $10^(-3)$, the standard Gibbs free energy change (in kJ) for this equilibrium is?

Thermodynamics

-168.7 TO -168.1

G-META-16-40

NUM

In vacuum degassing of steel, 14 ppm of dissolved nitrogen is in equilibrium with 1 mbar of nitrogen gas at 1873 K. At the same temperature, if the pressure is lowered to 0.7 mbar, the equilibrium nitrogen content (in ppm) is?

Thermodynamics

11.6 TO 11.8

G-META-17-32

NUM

Given: (i) Ambient temperature = 298K, (ii) emissivity of steel = 0.8, (iii) convective heat transfer coefficient = 4.6 $W.m^(-2).K^(-1), (iv) Stefan- Boltzmann constant(σ) = 5.7 * $10^(-8)W.m^(-2).k^(-4)$. A continuous cast steel slab, 1m * 1m * 0.1m, at 1298 K cools in air. The initial rate of heat loss (in KW) from the top surface of slab by radiation and convection is?(answer up to two decimal places)

Thermodynamics

130.00 TO 135.00