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An Fe/graphite diffusion couple is annealed at 1273 K. The carbon content (in mass %) on the Fe side of the Fe/graphite diffusion couple will be close to
A
0.5
B
1
C
1.6
D
6.7
Correct Answer:
6.7
What is the monoisotopic and average mass of valine? Given data: Mass of the most abundant isotope of Carbon (C°)=12.0000, Mass of most abundant isotope of Hydrogen (H°)=1.0078, Mass of most abundant isotope of Oxygen (O°)=15.9949, Mass of most abundant isotope of Nitrogen (N°)=14.0031, The average mass of Carbon (C)=12.011, The average mass of Hydrogen (H)=1.008, The average mass of Oxygen (O)=15.999, The average mass of Nitrogen (N)=14.007.
A
99.068 and 99.2361
B
99.216 and 99.326
C
99.111 and 99.321
D
99.068 and 99.132
It takes 10 hours to homogenize an alloy at 1273 K. The time required (in hours) to achieve the same extent of homogenization at 1373 K is . . . . . . . .
Given: Diffusivity, D
1373
K = 10
-18
m
2
s
-1
and D
1273
K = 10
-19
m
2
s
-1
A
0.5
B
1
C
2.5
D
4
The diffusion couple shown below is made from two A-B alloys. The initial compositions of the two alloys are indicated in the diagram. The centreline is at x = 0. The couple is held at an elevated temperature for 40 hours. Diffusivity; D = 3 × 10
-11
m
-2
s
-1
. Assume the diffusion couple to be infinitely long.
Which of the parameters give the composition profile in the following form?
$$C\left( {x,t} \right) + {c_1} + {c_2}\,erf\left( {\frac{1}{{2\sqrt {Dt} }}} \right)$$
A
c<sub>1</sub> = 0.45, c<sub>2</sub> = 0.05
B
c<sub>1</sub> = 0.5, c<sub>2</sub> = 0.4
C
c<sub>1</sub> = -0.05, c<sub>2</sub> = 0.45
D
c<sub>1</sub> = 0.1, c<sub>2</sub> = 0.9
In industries titanium is hardened through diffusion of carbon. The concentration of carbon at 1mm into the surface of the titanium slab is 0.25kg/m3 and at 3mm the concentration is 0.68kg/m3. The rate at which the carbon is entering into its surface is 1.27*10-9kg/m2.s. calculate the value of diffusion coefficient of carbon.
A
5.91*10-12
B
5.91*10-10
C
5.91*10-11
D
5.91*10-13
Combined carbon content in iron and steel is determined by treating the sample with dilute HNO
3
. So that combined carbon forms a soluble brown nitrated compound, the intensity of which is matched with that of a standard sample of similar composition treated under similar condition. The intensity of color produced is proportional to the carbon content of iron of steel sample. This method of combined carbon determination is called the
A
Strohlein method
B
Eggertz method
C
Combustion method
D
None of these
The two surfaces of a 5 mm thick plate of carbon steel are maintained at a carbon concentration of 10
4
mol. m
-3
on one side and zero concentration on the other side. Taking the diffusion coefficient of carbon in austenite to be 10
-11
m
-2
.s
-1
, the steady state flux (mol.m
-3
.s
-1
) through the thickness of the steel is
A
10<sup>-5</sup>
B
2 × 10<sup>-5</sup>
C
4 × 10<sup>-5</sup>
D
6 × 10<sup>-5</sup>
Consider the following statements regarding the importance of diffusion and choose the correct answer:
1. The exchange of gases takes place by the principle of dependent diffusion
2. The process of diffusion is involved in transpiration of water vapours
3. The ions are absorbed by the simple diffusion during passive salt uptake
4. Diffusion is an effective means of transport of substances over a very short distance and helps in the translocation of food materials
A
1, 3 and 4 are true
B
1 and 4 are true
C
1, 2 and 3 are true
D
2, 3 and 4 are true
An annealed plain carbon steel, showing fully pearlitic microstructure, has a carbon content of . . . . . . . . wt%.
A
0.01
B
0.20
C
0.77
D
1.20
A solid is being dried in the linear drying rate regime from moisture content X
o
to X
F
. The drying rate is zero at X = 0 and the critical moisture content is the same as the initial moisture X
o
. The drying time for M = (L
s
/AR
c
) is (where, L = total mass of dry solid, A = total surface area for drying R
c
= Constant maximum drying rate per unit area X = moisture content (in mass of water/mass of dry solids)
A
M (X<sub>o</sub> - X<sub>F</sub>)
B
M (X<sub>o</sub>/X<sub>F</sub>)
C
M ln(X<sub>o</sub>/X<sub>F</sub>)
D
MX<sub>o</sub> ln(X<sub>o</sub>/X<sub>F</sub>)
In a gas mixture of hydrogen and oxygen, steady state equimolar counter diffusion is occurring at a total pressure of 100 kPa and temperature of 20°C. If the partial pressures of oxygen at two planes 0.01 m apart, and perpendicular to the direction of diffusion are 15 kPa and 5 kPa, respectively and the mass diffusion flux of oxygen in the mixture is 1.6 * 10–5 kmol/m2.sec, calculate the molecular diffusivity for the system. For equimolar counter current diffusion:
A
2.898×10-5 m2/sec
B
3.898×10-5 m2/sec
C
2.989×10-5 m2/sec
D
3.989×10-5 m2/sec
