Mod 1 - Material (mass, moles) balance

Question 1

T/F: The Law of Conservation of Mass States that energy cannot be created nor destroyed.

Answer 1

FALSE: The law states this for MASS, although it is true for energy too.

Question 2

Define a BATCH process.

Answer 2

No mat (mass) transferred in/out of sys over time period of interest

Question 3

Define a CONTINUOUS process.

Answer 3

Mat (mass) transferred into and out of system continuously

Question 4

Define a SEMIBATCH process.

Answer 4

Any process that is neither batch nor continuous (ex. blend two liq in tank)

Question 5

Define TRANSIENT process.

Answer 5

Process variables change w/ time

Question 6

Define STEADY STATE process.

Answer 6

Process variables do not change w/ time (ex. V, P, flow rates)

Question 7

Classify process: Balloon is filled with air at steady rate of 2g/min

Answer 7

Semibatch, transient

Question 8

Classify process: Bottle of milk is taken from refrigerator and left on kitchen table.

Answer 8

Batch, transient

Question 9

Classify process: Water is boiled in open flask.

Answer 9

Semibatch, transient

Question 10

What is the full MB expression?

Answer 10

Acc = In - Out + Gen - Cons

Question 11

T/F: The generation and consumption terms are equal to zero if the system is at steady state.

Answer 11

FALSE: Accumulation is set to zero under this cond’t

Question 12

T/F: According to the Law of Conservation Mass, the gen - cons term should be equal to zero for MBs.

Answer 12

TRUE

Question 13

Outline the steps of an MB solution procedure.

Answer 13

1. Convert prob into PFD (what are in/out streams and their components?)
2. Label PFD w/ knowns, assign variables to unknowns, ID system to perform MB, decide on basis
3. Derive necessary equations from component and/or overall MB eq’ns + process constraint eq’ns
4. Check # of independent eq’ns (DoF)
5. Solve!

Question 14

T/F: System and control volume are synonymous.

Answer 14

FALSE

Question 15

T/F: Process may proceed in batch, semibatch or cont mode

Answer 15

TRUE

Question 16

T/F: General MB balance eq’n can only be solved when equals amnts of each comp are pres.

Answer 16

FALSE

Question 17

T/F: For non-reactive system at steady state, In = Out

Answer 17

TRUE

Question 18

T/F: if no stream amnts or flow rates are known, assumption for the basis of calculation must be made preferably for a stream of known components.

Answer 18

TRUE

Question 19

T/F: The maximum number of indep. eqn’s that can be written always equals the number of chemical species involved in the process.

Answer 19

FALSE: often, but not always

Question 20

T/F: The sol’t methodology dictates PCs be defined first

Answer 20

FALSE

Question 21

T/F: Always write all indep MBs as part of sol’t procedure

Answer 21

TRUE

Question 22

List all the components (preferably step form) you should include in solving MB probs.

Answer 22

1. Choose basis
2. Draw + fully label PFD
3. Write PCs
4. Perform DoF
5. Write all relev. MB eq’ns
6. Solve eq’ns for quant of interest
7. Check sol’n
8. Clearly present sol’n w/ proper units + sig figs