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 1350 kg/h · 25% sugarStream 2150 kg/h · 40% sugarStream 3ṁ₃ = ? kg/h

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

ṁ1 = 350 kg/hx1 = 25 %ṁ2 = 150 kg/hx2 = 40 %
ṁ3 = kg/h
2.Easy
MixerStream 1700 kg/h · 5% saltStream 2500 kg/h · 40% saltStream 3x₃ = ? %

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

ṁ1 = 700 kg/hx1 = 5 %ṁ2 = 500 kg/hx2 = 40 %
x3 = %
3.Medium
MixerStream 1950 kg/h · 50% saltStream 2ṁ₂ = ? · 10% saltProduct45% salt

How much of stream 2 must be added each hour to stream 1 so that the blended product contains 45% salt? Find ṁ2.

ṁ1 = 950 kg/hx1 = 50 %x2 = 10 %x3 = 45 %
ṁ2 = kg/h
4.Medium
MixerStream 1350 kg/h · 10% NaOHStream 2ṁ₂ = ? · 35% NaOHProduct20% NaOH

How much of stream 2 must be added each hour to stream 1 so that the blended product contains 20% NaOH? Find ṁ2.

ṁ1 = 350 kg/hx1 = 10 %x2 = 35 %x3 = 20 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F3900 kg/h · 12% NaOHProduct PP = ? · 45%Vapour W (pure water)0% NaOH

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

F = 3900 kg/hxF = 12 %xP = 45 %
P = kg/h
6.Hard
EvaporatorFeed F3600 kg/h · 11% 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 = 11 %xP = 30 %
P = kg/h

Answer key

  1. 1. ṁ3 = 500 kg/h
  2. 2. x3 = 19.58 %
  3. 3. ṁ2 = 135.7 kg/h
  4. 4. ṁ2 = 233.3 kg/h
  5. 5. P = 1040 kg/h
  6. 6. P = 1320 kg/h

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