1. What is the shape of the graph for steady state diffusion where the concentration of diffusion species is in the y-axis and position is in x-axis?
a) Parabola
b) Hyperbola
c) Ellipse
d) Straight line
Explanation: The concentration of the diffusing species is directly proportional to position. Hence graph is a straight line with negative slope.
2. In dilute aqueous solutions which of the following can be the value of diffusion coefficient at room temperature?
a) 0.7e-9
b) 0.7e-10
c) 2.2e-9
d) 2.2e-10
Explanation: The diffusion coefficient in a dilute aqueous medium for most ions lies in the range of 0.6e-9 to 2e-9 m2/s. Only 0.7e-9 lies in the range while the others are beyond the range and hence it is the answer.
3. There is no difference between diffusion and net diffusion.
a) True
b) False
Explanation: In homogeneous mixture diffusion and net diffusion are same but in case of in homogeneous materials the effect of diffusion is seen to be changing in concentration with time and hence in this case the net diffusion and diffusion values are different.
4. Which of the following law is used to non-steady state diffusion?
a) Fick’s first law
b) Fick’s second law
c) Bragg’s law
d) Charles’s law
Explanation: Fick’s second law is used to obtain the diffusion coefficient. Bragg’s law is used in diffraction of light while Charles’s law is used in thermodynamics and is also known as the law of volumes
5. Which of the following will diffuse the fastest in iron?
a) W
b) C
c) H
d) He
Explanation: Hydrogen due to its small size will diffuse the fastest in iron. Carbon also diffuses fast in iron which can be observed in carburizing of steel.
6. Which of the following law is a partial differential equation?
a) Fick’s first law
b) Fick’s second law
c) Bragg’s law
d) Charles’s law
Explanation: Fick’s second law is a partial differential law as it is defined as: On the right-hand side we have a partial differential of concentration with respect to time while on the left we have the product of diffusion constant and double partial differential of concentration with respect to the position in space.
7. Which of the following operator is used and on which side of Fick’s second law’s equation?
a) Laplacian operator, right hand side
b) Laplacian operator, left hand side
c) Curl operator, left hand side
d) Gradient, left hand side
Explanation: Laplacian operator whose symbol is Δ = ∇2, is used on the right side of the equation of Fick’s law. It replaces the double partial derivative of concentration with respect to space.
8. What is the dimension of d2c/dx2?
a) cm3
b) cm5
c) cm-3
d) cm-5
Explanation: The numerator has the dimension of cm-3 and the denominator has a dimension of cm2. Therefore, the quantity has a dimension of cm-3/cm2 which gives us cm-5 as the dimension.
9. Concentration gradient varies with time for which of the following processes?
a) Non-steady state diffusion
b) Osmosis
c) Steady state diffusion
d) Filter
Explanation: The concentration gradient varies with time for non-steady state diffusion. Meanwhile, it remains constant for steady state diffusion
10. In non-steady diffusion, a type of atom accumulates or depletes from a region.
a) True
b) False
Explanation: As the concentration gradient does not constant with respect to time. So the atoms get accumulated or depleted from certain regions from the system.