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 1850 kg/h · 10% saltStream 2500 kg/h · 30% saltStream 3ṁ₃ = ? kg/h

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

ṁ1 = 850 kg/hx1 = 10 %ṁ2 = 500 kg/hx2 = 30 %
ṁ3 = kg/h
2.Easy
MixerStream 1750 kg/h · 25% sugarStream 2500 kg/h · 20% sugarStream 3x₃ = ? %

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

ṁ1 = 750 kg/hx1 = 25 %ṁ2 = 500 kg/hx2 = 20 %
x3 = %
3.Medium
MixerStream 1700 kg/h · 45% sugarStream 2ṁ₂ = ? · 10% sugarProduct20% sugar

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

ṁ1 = 700 kg/hx1 = 45 %x2 = 10 %x3 = 20 %
ṁ2 = kg/h
4.Medium
MixerStream 1400 kg/h · 40% sugarStream 2ṁ₂ = ? · 20% sugarProduct25% sugar

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

ṁ1 = 400 kg/hx1 = 40 %x2 = 20 %x3 = 25 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F700 kg/h · 20% sugarProduct PP = ? · 55%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 = 700 kg/hxF = 20 %xP = 55 %
P = kg/h
6.Hard
EvaporatorFeed F600 kg/h · 20% NaOHProduct PP = ? · 35%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 = 600 kg/hxF = 20 %xP = 35 %
P = kg/h

Answer key

  1. 1. ṁ3 = 1350 kg/h
  2. 2. x3 = 23 %
  3. 3. ṁ2 = 1750 kg/h
  4. 4. ṁ2 = 1200 kg/h
  5. 5. P = 254.5 kg/h
  6. 6. P = 342.9 kg/h

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