Reaction Kinetics and Diffusion - Thermodynamics, Kinetics and Phase Transformations - Engineering Sciences Previous Year Questions

1

2007 · Engineering Sciences · Thermodynamics, Kinetics and Phase Transformations · Reaction Kinetics and Diffusion

Engineering Sciences (XE) 2007

In a material, which of the following diffusion mechanisms would have lowest activation energy ?

A

Lattice diffusion

B

Grain boundary diffusion

C

Surface diffusion

D

Diffusion through dislocations

Open complete paper

2

2008 · Engineering Sciences · Thermodynamics, Kinetics and Phase Transformations · Reaction Kinetics and Diffusion

Engineering Sciences (XE) 2008

The characteristic diffusion distance in a material with diffusivity “D” in time “t” is proportional to

A

Dt^1/2

B

D^1/2t

C

D^1/2t^1/2

D

Dt

Open complete paper

3

2008 · Engineering Sciences · Thermodynamics, Kinetics and Phase Transformations · Reaction Kinetics and Diffusion

Engineering Sciences (XE) 2008

The extent of reaction will be

A

0.90

B

0.95

C

0.99

D

1.00

Open complete paper

4

2011 · Engineering Sciences · Thermodynamics, Kinetics and Phase Transformations · Reaction Kinetics and Diffusion

Engineering Sciences (XE) 2011

It takes 4 h for carburising a steel at 900°C. If the same carburising is to be accomplished in 2 h, what should be the temperature? The activation energy of diffusion of carbon in the steel is 151 kJ mol^-1.

A

850°C

B

955°C

C

1015°C

D

1228°C

Open complete paper

5

2013 · Engineering Sciences · Thermodynamics, Kinetics and Phase Transformations · Reaction Kinetics and Diffusion

Engineering Sciences (XE) 2013

As temperature increases, diffusivity of an atom in a solid material,

A

increases

B

decreases

C

remains constant

D

depends on the specific material

Open complete paper

6

2014 · Engineering Sciences · Thermodynamics, Kinetics and Phase Transformations · Reaction Kinetics and Diffusion

Engineering Sciences (XE) 2014

The diffusion coefficients of Mg in Al at 500 and 550 °C are 1.9x10^-13 and 5.8x10^-13 m²/s respectively. The activation energy for diffusion of Mg in Al in kJ/mol is__________.

Check answer

Open complete paper

7

2015 · Engineering Sciences · Thermodynamics, Kinetics and Phase Transformations · Reaction Kinetics and Diffusion

Engineering Sciences (XE) 2015

The diffusion coefficient of copper atoms in aluminium is found to be 1.28 x 10^-22 m²s^-1 at T=400K and 5.75 x 10^-19 m²s^-1 at T=500K. Find the temperature (in Kelvin) at which the value of the diffusion coefficient is 10^-16 m²s^-1

Check answer

Open complete paper

8

2016 · Engineering Sciences · Thermodynamics, Kinetics and Phase Transformations · Reaction Kinetics and Diffusion

Engineering Sciences (XE) 2016

Gallium is to be diffused into pure silicon wafer such that its concentration at a depth of \(10^{-3}\) cm will be one half the surface concentration. Given that the diffusion coefficient (D) of gallium in silicon at 1355 °C is \(6 \times 10^{-11}\) cm\(^2\) s\(^{-1}\), the time the silicon wafer should be heated in contact with gallium vapour at 1355 °C is __________ s.
(Given: \(erf(0.5) \approx 0.5\))

Check answer

Open complete paper

9

2017 · Engineering Sciences · Thermodynamics, Kinetics and Phase Transformations · Reaction Kinetics and Diffusion

Engineering Sciences (XE) 2017

The value of diffusivity (D) for the diffusion of carbon (C) in γ-iron at 727 °C is………x10^-13 m²/s (Given D_o = 2x10^-5 m²/s; activation energy, Q = 142 kJ/mol; R = 8.314 J/mol. K)

Check answer

Open complete paper

10

2018 · Engineering Sciences · Thermodynamics, Kinetics and Phase Transformations · Reaction Kinetics and Diffusion

Engineering Sciences (XE) 2018

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 ______ K (round off to the nearest whole number)
(Given: Activation energy Q = 148 kJ mol⁻¹, Gas constant, R = 8.314 J mol⁻¹ K⁻¹)

Check answer

Open complete paper

11

2019 · Engineering Sciences · Thermodynamics, Kinetics and Phase Transformations · Reaction Kinetics and Diffusion

Engineering Sciences (XE) 2019

Copper is diffused into aluminium at 400 °C for 100 hours to obtain a certain concentration at a given depth. In another experiment conducted at 500 °C, to achieve the same concentration of copper at the same depth, the time required in hours is
(Given: Diffusion coefficients of copper in aluminium at 400 °C and 500 °C are 5 × 10⁻¹⁴ m² s⁻¹ and 6 × 10⁻¹³ m² s⁻¹, respectively)

A

7.33

B

8.33

C

9.33

D

10.33

Open complete paper

12

2020 · Engineering Sciences · Thermodynamics, Kinetics and Phase Transformations · Reaction Kinetics and Diffusion

Engineering Sciences (XE) 2020

A plain carbon steel sample containing 0.1 wt% carbon is undergoing carburization at 1100 °C in a carbon rich surroundings with fixed carbon content of 1.0 wt% all the time. The carburization time necessary to achieve a carbon concentration of 0.46 wt% at a depth of 5 mm at 1100 °C is ______ hour (round off to the nearest integer). Given: Diffusivity of carbon in iron at 1100 °C is 6.0 × 10⁻¹¹ m².s⁻¹ and

Check answer

Open complete paper

13

2022 · Engineering Sciences · Thermodynamics, Kinetics and Phase Transformations · Reaction Kinetics and Diffusion

Engineering Sciences (XE) 2022

It is known that component A diffuses into a solid to a depth of 10 μm in 1 hour at 300 K. Treat diffusion in one dimension. The time taken for A to diffuse to the same depth at 600 K is __________ seconds. (Round off to 1 decimal).
Diffusivity of A in the solid is given by
\[ D_A = D_A^0 \exp\left(-\frac{E_a}{k_B T}\right) \]
\( D_A^0 \): Diffusivity coefficient
\( E_a \): Activation energy = 0.3 eV
\( k_B \): Boltzmann’s constant = 8.62×10⁻⁵ eV/K
\( T \): Absolute temperature

Check answer

Open complete paper

14

2023 · Engineering Sciences · Thermodynamics, Kinetics and Phase Transformations · Reaction Kinetics and Diffusion

Engineering Sciences (XE) 2023

A metal has a certain vacancy fraction at a temperature of 600 K. On increasing the temperature to 900 K, the vacancy fraction increases by a factor of ______ (rounded off to one decimal place)
Given: Gas constant, R = 8.31 J mol^{-1}K^{-1} and activation energy for vacancy formation, Q = 68 kJ mol^{-1}

Check answer

Open complete paper

15

2023 · Engineering Sciences · Thermodynamics, Kinetics and Phase Transformations · Reaction Kinetics and Diffusion

Engineering Sciences (XE) 2023

A pure Silicon wafer is doped with Boron by exposing it to \(B_2O_3\) vapour at an elevated temperature. It takes 1000 seconds to reach a Boron concentration of \(10^{20} atoms\ m^{-3}\) at a depth of 1 \(\mu m\). The time taken to reach the same concentration of Boron at a depth of 2 \(\mu m\) is (in seconds): __________ (rounded off to nearest integer) Given: Boron concentration on the wafer surface remains constant.

Check answer

Open complete paper

16

2024 · Engineering Sciences · Thermodynamics, Kinetics and Phase Transformations · Reaction Kinetics and Diffusion

Engineering Sciences (XE) 2024

Given that k is the first order reaction rate constant and T is the temperature in absolute scale, the temperature dependence of rate constant is/are represented by

A

Graph (A): k vs T showing an exponential increase.

B

Graph (B): k vs T showing a curve that increases and then plateaus.

C

Graph (C): ln k vs 1/T showing a straight line with positive slope.

D

Graph (D): ln k vs 1/T showing a straight line with negative slope.

Check answer

Open complete paper

17

2026 · Engineering Sciences · Thermodynamics, Kinetics and Phase Transformations · Reaction Kinetics and Diffusion

Engineering Sciences (XE) 2026

Which of the following statements is/are applicable to Fick’s second law:

A

Concentration changes with time

B

Steady state condition prevails

C

Diffusion is time dependent

D

Concentration profile is linear

Check answer

Open complete paper

18

2026 · Engineering Sciences · Thermodynamics, Kinetics and Phase Transformations · Reaction Kinetics and Diffusion

Engineering Sciences (XE) 2026

A radioactive isotope sample has a decay constant \(\lambda = 2.31 \times 10^{-4} \text{ year}^{-1}\). Initially the sample contains \(8000 \times 10^{15}\) atoms. The sample decays to 25% of its initial value. The number of years it takes to decay to this stage is closest to __________

A

3000

B

6000

C

900

D

2600

Open complete paper