CHEMICAL ENGINEERING PRINCIPLES
1 QUESTIONS AND VERIFIED
ANSWERS|100% CORRECT|GRADE A+
Law of Conservation of Mass and Energy - ANSWER All transfers of mass must remain constant, it can
neither be created or destroyed. What this means for chemical engineers is that what must go into a
system must come out of a system
Base Units - ANSWER describe length, mass, time [m, kg, s]
Multiple Units - ANSWER density, volume etc. [g/cm^3, g/L]
Compound Units - ANSWER units when put together make up another unit, force [Pa = N/m^2]
Governing equation for mass balances - ANSWER dM/dt = Min-Mout+Mgen-Mcon
Absolute Pressure - ANSWER Pressure relative to a perfect vacuum or pressure deviation from perfect
vacuum. so a reading of x means a perfect vacuum,can not be less than x.
Gauge Pressure - ANSWER Pressure relative to atmospheric pressure, or pressure deviation from
atmospheric pressure. so a reading of x means no deviation from atmosphere, a negative reading means
pulling a vacuum.
Atmospheric Pressure - ANSWER Pressure at the base of a column of fluid at the point of measurement.
E.g. air at sea level = 1 atm (760 mmHg)
Differential Manometer - ANSWER used to measure the pressure difference between two points in a
process line. P1-P2=(pf-p)gh
Three different types of chemical processes for reactor designs - ANSWER Batch, continuous, semi-batch
, Batch - ANSWER Materials placed into the tank at the beginning of the process and materials removed
sometime later. Between the time, no mass crosses the system boundary.
Continuous - ANSWER Process flows continuously at steady state, no change in mass over time, example:
distillation
Semi-batch - ANSWER one material flows continuously while another material sits in a tank. any process
that is neither batch nor continuous.
Stack Gas - ANSWER product gas leaving a combustion furnace. By analyzing stack gas we can calculate
composition on a dry and wet basis. Necessary for improving fuel efficiency and reducing undesirable
exhaust emissions
Wet stack gas - ANSWER mole fraction composition of gas including H2O
Dry stack gas - ANSWER mole fraction composition of gas without H2O
3 different methods used as material balance - ANSWER mass balance, atomic balance, species balance
is beneficial because reactive species are just in=out, with extent of reaction nout=nin+V(extent) V (are
stoic coefficients)
Why would you want a recycle stream? - ANSWER A recycle stream can save money by avoiding wasting
resources that are included in the fresh feed but not as a product. Spend less money on the fresh feed
and sell the purified product at a higher price.
Why would you want a purge stream? - ANSWER A purge stream would want to be used to add
accumulation of a material that has no way of exiting the system as a product. to prevent build up in the
system and recycle stream.
Complete combustion - ANSWER when all of the limiting reactant is used
incomplete combustion - ANSWER when not all of the limiting reactant is used
1 QUESTIONS AND VERIFIED
ANSWERS|100% CORRECT|GRADE A+
Law of Conservation of Mass and Energy - ANSWER All transfers of mass must remain constant, it can
neither be created or destroyed. What this means for chemical engineers is that what must go into a
system must come out of a system
Base Units - ANSWER describe length, mass, time [m, kg, s]
Multiple Units - ANSWER density, volume etc. [g/cm^3, g/L]
Compound Units - ANSWER units when put together make up another unit, force [Pa = N/m^2]
Governing equation for mass balances - ANSWER dM/dt = Min-Mout+Mgen-Mcon
Absolute Pressure - ANSWER Pressure relative to a perfect vacuum or pressure deviation from perfect
vacuum. so a reading of x means a perfect vacuum,can not be less than x.
Gauge Pressure - ANSWER Pressure relative to atmospheric pressure, or pressure deviation from
atmospheric pressure. so a reading of x means no deviation from atmosphere, a negative reading means
pulling a vacuum.
Atmospheric Pressure - ANSWER Pressure at the base of a column of fluid at the point of measurement.
E.g. air at sea level = 1 atm (760 mmHg)
Differential Manometer - ANSWER used to measure the pressure difference between two points in a
process line. P1-P2=(pf-p)gh
Three different types of chemical processes for reactor designs - ANSWER Batch, continuous, semi-batch
, Batch - ANSWER Materials placed into the tank at the beginning of the process and materials removed
sometime later. Between the time, no mass crosses the system boundary.
Continuous - ANSWER Process flows continuously at steady state, no change in mass over time, example:
distillation
Semi-batch - ANSWER one material flows continuously while another material sits in a tank. any process
that is neither batch nor continuous.
Stack Gas - ANSWER product gas leaving a combustion furnace. By analyzing stack gas we can calculate
composition on a dry and wet basis. Necessary for improving fuel efficiency and reducing undesirable
exhaust emissions
Wet stack gas - ANSWER mole fraction composition of gas including H2O
Dry stack gas - ANSWER mole fraction composition of gas without H2O
3 different methods used as material balance - ANSWER mass balance, atomic balance, species balance
is beneficial because reactive species are just in=out, with extent of reaction nout=nin+V(extent) V (are
stoic coefficients)
Why would you want a recycle stream? - ANSWER A recycle stream can save money by avoiding wasting
resources that are included in the fresh feed but not as a product. Spend less money on the fresh feed
and sell the purified product at a higher price.
Why would you want a purge stream? - ANSWER A purge stream would want to be used to add
accumulation of a material that has no way of exiting the system as a product. to prevent build up in the
system and recycle stream.
Complete combustion - ANSWER when all of the limiting reactant is used
incomplete combustion - ANSWER when not all of the limiting reactant is used
