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Quizzes > Engineering & Technology

Principles Of Che Quiz

Free Practice Quiz & Exam Preparation

Difficulty: Moderate
Questions: 15
Study OutcomesAdditional Reading
3D voxel art representation of the Principles of CHE course material

This Principles of CHE quiz helps you practice material and energy balances, process calculations, and problem solving. Work through 15 quick questions to see what's solid and what needs work. Use your results to focus review before class or exams.

What is the primary principle behind material balances in process calculations?
Conservation of energy
Conservation of mass
Conservation of charge
Conservation of momentum
The material balance is based on the conservation of mass principle, which states that mass is neither created nor destroyed. This fundamental concept is essential in designing and analyzing chemical processes.
In a steady-state system, what is true regarding the accumulation of a substance?
The accumulation is positive
The accumulation is zero
The accumulation equals the rate of reaction
The accumulation is negative
A steady-state system indicates that the amount of material remains constant over time, meaning there is no net accumulation. Thus, the accumulation term is zero.
Which fundamental law underpins the energy balance used in chemical process calculations?
The second law of thermodynamics
The first law of thermodynamics
The conservation of momentum
Newton's second law
Energy balances are based on the first law of thermodynamics, which asserts that energy cannot be created or destroyed, only transformed. This law is critical to understanding how energy is distributed within a system.
Material balances are essential in process design because they help determine which of the following?
System mass flow rates
Pressure drops across equipment
Reaction equilibrium constants
Heat transfer coefficients
Material balances are used to calculate the rate at which mass enters and leaves a process unit, enabling the determination of system mass flow rates. This information is vital for sizing equipment and ensuring process efficiency.
In an energy balance, which term primarily represents the energy change due to phase transitions and chemical reactions?
Kinetic energy
Potential energy
Heat of reaction
Electrical energy
The heat of reaction accounts for the energy absorbed or released during chemical reactions and phase changes. This term is essential in energy balance calculations as it directly affects the system's thermal behavior.
In a dynamic reactor material balance that includes inlet streams, outlet streams, and generation due to reaction, which term is added to account for system changes?
Friction loss term
Accumulation term
Viscous dissipation term
Scale factor term
In a dynamic (unsteady state) analysis, the accumulation term represents the rate of change of mass within the system. This term is omitted in steady-state calculations but is crucial when system properties change over time.
When applying a material balance to a flash separation process, which approach is most appropriate?
Performing a global balance and separate phase balances
Focusing solely on the energy balance
Balancing only the liquid phase
Balancing only the vapor phase
A flash separation involves both vapor and liquid phases; therefore, a global material balance is set up followed by individual balances for each phase. This dual approach ensures accurate determination of phase compositions.
What is a primary challenge when performing material balances for processes with recycle streams?
Solving simultaneous equations due to interconnected recirculation
Accounting for pressure drops exclusively
Neglecting reaction stoichiometry
Ignoring thermal effects
Recycle streams create loops in the process, leading to simultaneous equations that must be solved to account for the interdependency of mass flows. This complexity is a common challenge in obtaining accurate material balances.
In a transient material balance analysis, what does the accumulation term specifically represent?
Mass loss due to leaks
The constant mass entering the system
Fixed mass distribution among phases
The time rate of change of mass within the system
The accumulation term quantifies how mass within a control volume changes with time, making it a critical part of transient analyses. It captures the net difference between inflow, outflow, and reaction rates over time.
For a closed system undergoing an exothermic reaction, which factor is most critical in the energy balance?
The heat generated by the reaction
Momentum of reactant streams
System color change
Ambient temperature variations
In a closed system, the energy released due to the exothermic reaction directly affects the temperature and energy balance of the system. Accurately capturing this heat generation is essential for proper energy analysis.
Which analytical technique is commonly used to manage complexities in material and energy balances around a control volume?
Static pressure evaluation
Isotherm mapping
Dimensional analysis alone
Control volume analysis
Control volume analysis simplifies the process by focusing on a defined region where mass and energy fluxes are analyzed across the boundaries. This approach facilitates the development of balance equations in complex systems.
When combining material and energy balances in reactor analysis, which additional consideration is typically required?
Evaluating Coriolis force effects
Incorporating reaction kinetics
Including magnetic field interactions
Focusing solely on gravitational effects at high altitude
Reaction kinetics links the rate of consumption and production of species with both material and energy changes. This factor is vital for predicting reactor performance when combining these balances.
In an exothermic reactor system, why might a sudden temperature increase lead to a re-evaluation of the material balance?
Because it causes a decrease in material flow rates due to compression
Because increased temperature can alter reaction rates and conversion levels
Because it suddenly creates additional mass
Because it changes the underlying conservation laws
A rise in temperature in an exothermic reactor generally increases the reaction rate, thereby changing the conversion and product distribution. Such changes necessitate an updated material balance to accurately reflect the new operating conditions.
How does reaction stoichiometry influence material balance calculations in multiphase reactors?
It only affects the energy balance, not the material balance.
It provides the necessary molar relationships between reactants and products for closure of the balance.
It is irrelevant when multiple phases are present.
It is used primarily for hydraulic design considerations.
Reaction stoichiometry determines the quantitative relationships between reactants and products. This information is critical to closing material balances, especially in multiphase systems where species distribute differently.
Which factor most significantly complicates the energy balance in a reactor where chemical reactions and phase changes occur simultaneously?
The precise measurement of reactant flow rates
Variations in phase color
Pressure drop across the reactor
The interplay between sensible heat, latent heat, and reaction heat
When reactions and phase changes occur concurrently, the energy balance must account for sensible heat changes, latent heat from phase transitions, and the heat of reaction. The interaction of these factors adds significant complexity to the analysis.
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Study Outcomes

  1. Analyze material balance equations in chemical processes.
  2. Apply energy balance principles to solve process problems.
  3. Evaluate conservation of mass and energy in real-world scenarios.
  4. Perform calculations to determine material and energy efficiencies.

Principles Of Che Additional Reading

Ready to dive into the world of material and energy balances? Here are some top-notch resources to guide your journey:

  1. This comprehensive resource offers syllabi, course notes, screencasts, and digital tools from various universities, providing a well-rounded understanding of material and energy balances.
  2. Curated by IIT Madras, this collection includes lecture notes, question papers, multiple-choice questions, presentations, and videos, covering topics from basic terminologies to unsteady-state processes.
  3. Featuring 155 video lectures from the University of Colorado, this series delves into unit conversions, material balance problems, and energy balances, offering practical examples and problem-solving techniques.
  4. This textbook presents balance concepts and calculations in an accessible format, with 70 worked examples connecting process balances to contemporary material and energy concerns.
  5. This teaching module provides lecture notes on mass and energy balances, covering key topics such as dimensions, units, unit conversion, material balances, and energy balances.
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