# Chemical Reaction Engineering Questions and Answers – Non Ideal Flow Basics – Properties of C, F and E Curves – 2

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This set of Chemical Reaction Engineering Questions and Answers for Experienced people focuses on “Non Ideal Flow Basics – Properties of C, F and E Curves – 2”.

1. Which of the following is not a characteristic of tracer?
a) Inertness
b) Non – reactive
c) Easily detectable
d) Adsorbance onto the reactor surface

Explanation: The tracer should not stick to the walls or other surfaces of reactor. The physical properties of the tracer should be similar to that of the system.

2. If the exit age distribution is given as δ(t – 4), then $$\int_0^∞$$ t2 E(t)dt is ____
a) 16
b) 4
c) 8
d) 20

Explanation: Exit age distribution is represented by dirac delta function. $$\int_0^∞$$ δ(t-τ)f(t)dt = f(τ). Hence, $$\int_0^∞$$ t2 E(t)dt = 42 = 16.

3. If C=2 and area under the C – curve is 4 for a pulse input, then the value of E is ____
a) 2
b) 0.5
c) 1
d) 8

Explanation: E = $$\frac{C}{\int_0^∞ C dt}$$
$$\int_0^∞$$ C dt is the area under the C – curve. Hence, E = $$\frac{2}{4}$$ = 0.5.
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4. The F(t) function for a PFR is _____
a) F(t) = $$\begin{cases} 0 & for & 0 < t < \overline{t}, \\ ∞ & for & t > \overline{t}\\ \end{cases}$$
b) F(t) = $$\begin{cases} 1 & for & 0 < t < \overline{t}, \\ 0 & for & t > \overline{t}\\ \end{cases}$$
c) F(t) = $$\begin{cases} 0 & for & 0 < t < \overline{t}, \\ 1 & for & t > \overline{t}\\ \end{cases}$$
d) F(t) = $$\begin{cases} ∞ & for & 0 < t < \overline{t}, \\ 1 & for & t > \overline{t}\\ \end{cases}$$

Explanation: The plug flow reactor has no longitudinal mixing. Hence, all fluid elements leaving the reactor have the same age (t).

5. Which of the following represents area under the C – curve? (Where, M is the total amount of tracer injected and
v is the volumetric flow rate of the effluent)
a) $$\frac{M}{v}$$
b) $$\frac{v}{M}$$
c) M × v
d) M × V

Explanation: Carea = $$\frac{M}{v}$$. The unit is (kg.s)/m3.

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