Engineering Questions with Answers - Multiple Choice Questions
Environmental Engineering MCQ’s – Kinetics of Chemical Disinfection
1 - Question
Consider the following variables.
i. Concentration of disinfectant
ii. Concentration of organisms
iii. Temperature
iv. Time of contact
Disinfection is the function of which of the following variables?
a) i, ii
b) i, ii, iii
c) i, ii, iii, iv
d) ii, iii, iv
View Answer
Answer: c
Explanation: The process of disinfection is the function of concentration of disinfectant, organisms, temperature of disinfection and time of contact.
Explanation: The process of disinfection is the function of concentration of disinfectant, organisms, temperature of disinfection and time of contact.
2 - Question
According to which of the following, organism destroyed by disinfection is proportional to organism remaining?
a) Hazens equation
b) Chicks law
c) Darcy’s law
d) Rose equation
View Answer
Answer: b
Explanation: According to Chicks law of disinfection, the number of organisms destroyed in unit time is proportional to the number of organisms remaining.
3 - Question
Which of the following is the expression of Chicks law?
a) Dy/Dt = k (N – y)
b) Dy/Dt = k/(N – y)
c) Dy/Dt = k (N + y)
d) Dy/Dt = k (N * y)
View Answer
Answer: a
Explanation: The expression of Chicks law is given by Dy/Dt = k (N – y) Where, N is the number of organisms initially present, ‘y’ is the number of organisms remaining after time t and k is the coefficient of proportionality.
4 - Question
The integration of the expression of Chicks law is given by ____________
a) N1/N = ekt
b) N1/N = kt
c) N1/N = k/t
d) N1/N = e-kt
View Answer
Answer: d
Explanation: According to Chicks law, Dy/Dt = k (N – y), by integration,
loge N1/N = -kt
= N1/N = e-kt Where, N1 = N – y.
5 - Question
The dimensional formula of rate constant used in Chicks law is ____________
a) 1/t
b) 1/t2
c) 1/t3
d) t2
View Answer
Answer: a
Explanation: According to Chicks law, Dy/Dt = k (N – y) where, k is the rate of proportionality or rate constant having dimensional formula 1/t.
6 - Question
The number of organisms destroyed is equal to the number of organisms remaining at time t = __________
a) 0
b) 1
c) 2
d) 10
View Answer
Answer: a
Explanation: According to Chicks law, N1/N = e-kt, when t=0,
N1/N = 1 or N1 = N, Where, N1 represents the remaining organisms.
7 - Question
The expression loge N1/N = – kt m Where m is a constant such that m>1 represents ____________
a) Rate of the kill will remains constant with time
b) Rate of the kill will increase with time
c) Rate of the kill will decrease with time
d) Rate of the kill is directly proportional to time
View Answer
Answer: b
Explanation: The expression loge N1/N = -ktm Where m is a constant such that m>1 represents that rate of kill will increase with time whereas m<1 represents rate of the kill decrease with time.
8 - Question
For changing the concentration of disinfectant, the disinfecting efficiency is expressed by ____________
a) C n *t p = Constant
b) C n/ t p = Constant
c) C q * Np = Constant
d) C q / Np = Constant
View Answer
Answer: a
Explanation: The disinfecting efficiency is expressed by C n *t p = Constant where, C is the concentration of disinfectant, t p is the time required to kill the organism and n is the coefficient of dilution.
9 - Question
The number of organisms in disinfection process can be expressed by ____________
a) Cn *t p = Constant
b) C n / tp = Constant
c) C q * Np = Constant
d) C q / Np = Constant
View Answer
Answer: c
Explanation: The number of organisms in disinfection process can be expressed by Cq * Np = Constant where, C is the concentration of disinfectant, the Np is the reduced concentration of organisms and q is the coefficient of disinfectant strength.
10 - Question
Efficiency of dilution decreases rapidly when the coefficient of dilution is ____________
a) 0
b) 1
c) <1
d) >1
View Answer
Answer: d
Explanation: Efficiency of dilution decreases rapidly when the coefficient of dilution n is greater than 1 which is a measure of order of reaction.
11 - Question
When the coefficient of dilution is 1, then which of the following statement is correct?
a) Time of contact is more important than dosage
b) The dosage is more important than time of contact
c) Concentration and time are equally important
d) Efficiency of dilution decreases.
View Answer
Answer: c
Explanation: When the coefficient of dilution is 1, concentration and time are equally important and a first order will proceed.
12 - Question
The temperature of disinfection is inversely proportional to the killing of organisms.
a) True
b) False
View Answer
Answer: b
Explanation: The temperature of disinfection is directly proportional to the killing of organisms and the increase in temperature results in more rapid killing of organisms.