GATE ES topic:kinetics-reactor-design PYQs & Answers

Questions 1–10 of 13. Imported answers require independent review unless marked reviewed.

Reaction A → B follows first-order element kinetics and the reaction rate constant for A is 0.01 per min. The time taken to reduce the concentration of A from 100 M to 10 M in a batch reactor is ______ min (rounded off to one decimal place).

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A continuous flow stirred tank reactor (CSTR) operates under a steady-state condition with a flow rate of 300 L per hour. The influent concentration of a substrate entering the reactor is 150 mg/L.

To give a treatment efficiency of 76% for the substrate that decays according to half-order kinetics with a rate constant of 0.05 (mg/L)

per hour, the required volume of the reactor is _____ m

(answer in integer).

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Match the following and choose the correct option from the following

Type of reactor	Diagram
1. Plug flow reactor	x.
2. Continuously stirred tank reactor	y.
3. Batch reactor	z.

The stirrer symbol indicates stirrer for mixing (not to scale).

Your answerChoose one option.

1-x, 2-y, 3-z

1-z, 2-y, 3-x

1-y, 2-z, 3-x

1-x, 2-z, 3-y

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Consider the following figure of an activated sludge process (ASP), depicting the flow (

), substrate (

), and microorganism concentration (

) at various points in the system, where subscripts “0”, “r”, “w”, “e”, and “i” indicate influent, recycle line, wastage, effluent, and flow from aeration tank to settling tank, respectively. Note that influent to the ASP has microbes too. V is volume of aeration tank.

Diagram for Environmental Science and Engineering question 39

Choose the correct option for net rate of formation of microorganisms in the system at steady state, from the following

Your answerChoose one option.

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You conducted a batch experiment in the lab for 10 minutes to degrade a toxic compound, which follows first order kinetics. The compound degrades from

M to

M. The information from the lab experiment will be used to design a plug flow reactor in field conditions.

Given field conditions: • Flow rate of contaminated water to be treated: 1 m³/hour • Concentration of toxic compound in contaminated water:

M • Target concentration of toxic compound in treated water:

M • Temperature is same in lab and field conditions.

The required volume of the plug flow reactor is ________ m³. (rounded off to two decimal places)

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Consider second order kinetics (

) under steady state condition. The ratio of volume of a complete mixed reactor (CMR) to that of a plug flow reactor (PFR) to achieve 90% reduction in the concentration is ______.

Inlet concentrations in both the reactors are same.

Your answerChoose one option.

10.0

1.0

0.1

2.3

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A biological reactor is getting wastewater containing 1 mole/L acetate ions as carbon source. The following reaction takes place in the bio-reactor:

Assume that all acetate ions are consumed and ammonia serves as a nutrient source. Given that 1 g acetate exerts 1.07 g COD; 1 mole bacteria =113 g VSS; 1 mole acetate ion = 59 g. Value of observed yield is ________________ (in g VSS/g COD, rounded off to two decimal places).

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An aeration tank needs to be installed for the removal of VOC from water, where the required rate of flow of water through the aeration tank is 180,000 m³/d. Permissible limit of VOC in the water is 12 μg/L. The saturation concentration of VOC is 5 μg/L and gas transfer rate constant is 0.40 per second at 25 °C. The initial concentration of VOC in the water is 33 μg/L. The volume of the aeration tank to satisfy the permissible limit of VOC at 25 °C is ________________(in m³, rounded off to two decimal places).

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Which one of the following statements is NOT correct with respect to a batch reactor?

Your answerChoose one option.

No reactant is added after the reactor has started operation.

No product is withdrawn during the course of the reactor operation.

The reactor operates under steady state.

The reactor operation is carried out for a pre-specified duration.

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Which of the following statement(s) is/are NOT correct while comparing continuously stirred tank reactor (CSTR) and plug flow reactor (PFR)?

Your answerSelect all correct options. You can choose more than one.

CSTR and PFR are normally operated under steady state condition.

There is complete homogeneity in the CSTR while there are concentration variations within the PFR.

The overall reaction carried out in a PFR is always higher than that in a CSTR for same total volume.

Reaction kinetics do not play any role in choosing between a CSTR and PFR.

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GATE ES topic:kinetics-reactor-design PYQs

How to practice topic:kinetics-reactor-design

Question 50

Question 59

Question 18

Question 39

Question 57

Question 39

Question 55

Question 65

Question 40

Question 46