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 1500 kg/h · 40% saltStream 2300 kg/h · 30% saltStream 3x₃ = ? %

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

ṁ1 = 500 kg/hx1 = 40 %ṁ2 = 300 kg/hx2 = 30 %
x3 = %
2.Easy
MixerStream 1150 kg/h · 15% sugarStream 2800 kg/h · 20% sugarStream 3ṁ₃ = ? kg/h

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

ṁ1 = 150 kg/hx1 = 15 %ṁ2 = 800 kg/hx2 = 20 %
ṁ3 = kg/h
3.Medium
MixerStream 1750 kg/h · 15% sugarStream 2ṁ₂ = ? · 40% sugarProduct35% sugar

How much of stream 2 must be added each hour to stream 1 so that the blended product contains 35% sugar? Find ṁ2.

ṁ1 = 750 kg/hx1 = 15 %x2 = 40 %x3 = 35 %
ṁ2 = kg/h
4.Medium
MixerStream 1350 kg/h · 20% saltStream 2ṁ₂ = ? · 50% saltProduct35% salt

How much of stream 2 must be added each hour to stream 1 so that the blended product contains 35% salt? Find ṁ2.

ṁ1 = 350 kg/hx1 = 20 %x2 = 50 %x3 = 35 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F3900 kg/h · 14% saltProduct PP = ? · 30%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 = 3900 kg/hxF = 14 %xP = 30 %
P = kg/h
6.Hard
EvaporatorFeed F600 kg/h · 7% sugarProduct PP = ? · 50%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 = 600 kg/hxF = 7 %xP = 50 %
P = kg/h

Answer key

  1. 1. x3 = 36.25 %
  2. 2. ṁ3 = 950 kg/h
  3. 3. ṁ2 = 3000 kg/h
  4. 4. ṁ2 = 350 kg/h
  5. 5. P = 1820 kg/h
  6. 6. P = 84 kg/h

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