Batch Reactor Design Questions and Answers

Answer: C

The flexibility of a batch vessel suits fine chemicals and pharmaceuticals where campaigns are short. Continuous operation wins whenever one product is made in quantity for a long period. Campaign length decides the choice.

Answer: D

The first two are correct. The third is the wrong way round, since each batch may differ slightly from the last while a continuous reactor at steady state produces a constant output. Uniformity is where continuous operation wins.

Answer: A

Each batch is a separate experiment and small differences in charging, timing or temperature show up in the product. Continuous operation at steady state avoids this by construction. Careful procedure reduces but never removes it.

Answer: B

Correct answer: one minus the concentration ratio

At constant volume the moles and the concentrations are proportional, so \[ X = 1 - \frac{C_A}{C_{A0}}. \] The ratio itself is the fraction *remaining* rather than the fraction converted, which is the option offered beside the key. The relation fails at varying volume, where the mole form must be used instead.

Answer: C

Both are true and the reason gives the necessity: concentration is moles over volume, so both the numerator and the denominator change and the simple constant volume relations no longer hold. Liquid phase reactions are usually constant volume.

Answer: D

There are no flowing streams in a batch reactor, which is exactly what distinguishes its energy balance from that of a flow reactor. The other three are the three terms that actually appear. The absence of flow is what defines the batch case.

Answer: A

Volume grows with the cube of the linear dimension and jacket area only with the square, so the area per unit volume falls. Internal coils or an external loop are the usual remedies. The ratio falls in proportion to the linear dimension.

Answer: B

Both are true and the reason gives the mechanism: the same reaction generates heat in proportion to volume while the cooling capacity grows only with area, which is the classic scale-up hazard. Calorimetry is what settles the question in advance.

Answer: C

Correct answer: 4

Volume scales with the cube of a linear dimension and area with the square, so an eightfold volume means a linear factor of \( 8^{1/3}=2 \) and an area factor of \( 2^{2}=4 \). The heat to be removed rises with the volume and the surface available to remove it with the area, so the cooling per unit of contents falls by half - which is why a reaction that is manageable in the laboratory can be dangerous in a plant vessel.

Answer: D

Correct answer: True

Feeding one reactant gradually means only a little is present at any moment, so the reaction rate - and therefore the rate of heat release - is limited by the feed rate rather than by the kinetics. The operator controls the exotherm with a valve, and stopping the feed stops the heat almost at once. It is the standard answer to a reaction whose adiabatic temperature rise the vessel could not survive.