Mass balance worksheet with answers

Free printable Mass balance worksheet: 6 problems from easy to exam level, with an answer key. Print it or save it as a PDF.

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1.Easy
MixerStream 11000 kg/h · 5% saltStream 2850 kg/h · 35% saltStream 3x₃ = ? %

Two salt solutions are mixed at steady state. Find the mass fraction of salt in the outlet x3.

ṁ1 = 1000 kg/hx1 = 5 %ṁ2 = 850 kg/hx2 = 35 %
x3 = %
2.Easy
MixerStream 1100 kg/h · 30% NaOHStream 2900 kg/h · 5% NaOHStream 3ṁ₃ = ? kg/h

Two NaOH solutions are mixed at steady state. Find the outlet flow rate ṁ3.

ṁ1 = 100 kg/hx1 = 30 %ṁ2 = 900 kg/hx2 = 5 %
ṁ3 = kg/h
3.Medium
MixerStream 1650 kg/h · 20% NaOHStream 2ṁ₂ = ? · 45% NaOHProduct30% NaOH

How much of stream 2 must be added each hour to stream 1 so that the blended product contains 30% NaOH? Find ṁ2.

ṁ1 = 650 kg/hx1 = 20 %x2 = 45 %x3 = 30 %
ṁ2 = kg/h
4.Medium
MixerStream 1700 kg/h · 5% saltStream 2ṁ₂ = ? · 30% saltProduct25% salt

How much of stream 2 must be added each hour to stream 1 so that the blended product contains 25% salt? Find ṁ2.

ṁ1 = 700 kg/hx1 = 5 %x2 = 30 %x3 = 25 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F2900 kg/h · 11% saltProduct PP = ? · 60%Vapour W (pure water)0% salt

An evaporator concentrates a salt solution by boiling off pure water. Find the product flow P in kg/h.

F = 2900 kg/hxF = 11 %xP = 60 %
P = kg/h
6.Hard
EvaporatorFeed F3600 kg/h · 5% sugarProduct PP = ? · 30%Vapour W (pure water)0% sugar

An evaporator concentrates a sugar solution by boiling off pure water. Find the product flow P in kg/h.

F = 3600 kg/hxF = 5 %xP = 30 %
P = kg/h

Answer key

  1. 1. x3 = 18.78 %
  2. 2. ṁ3 = 1000 kg/h
  3. 3. ṁ2 = 433.3 kg/h
  4. 4. ṁ2 = 2800 kg/h
  5. 5. P = 531.7 kg/h
  6. 6. P = 600 kg/h

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