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 1950 kg/h · 35% sugarStream 2950 kg/h · 5% sugarStream 3x₃ = ? %

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

ṁ1 = 950 kg/hx1 = 35 %ṁ2 = 950 kg/hx2 = 5 %
x3 = %
2.Easy
MixerStream 1900 kg/h · 10% saltStream 2800 kg/h · 40% saltStream 3x₃ = ? %

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

ṁ1 = 900 kg/hx1 = 10 %ṁ2 = 800 kg/hx2 = 40 %
x3 = %
3.Medium
MixerStream 1950 kg/h · 50% saltStream 2ṁ₂ = ? · 20% saltProduct40% salt

How much of stream 2 must be added each hour to stream 1 so that the blended product contains 40% salt? Find ṁ2.

ṁ1 = 950 kg/hx1 = 50 %x2 = 20 %x3 = 40 %
ṁ2 = kg/h
4.Medium
MixerStream 1400 kg/h · 35% sugarStream 2ṁ₂ = ? · 5% 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 = 400 kg/hx1 = 35 %x2 = 5 %x3 = 20 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F800 kg/h · 5% sugarProduct PP = ? · 60%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 = 800 kg/hxF = 5 %xP = 60 %
P = kg/h
6.Hard
EvaporatorFeed F3600 kg/h · 18% NaOHProduct PP = ? · 50%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 = 3600 kg/hxF = 18 %xP = 50 %
P = kg/h

Answer key

  1. 1. x3 = 20 %
  2. 2. x3 = 24.12 %
  3. 3. ṁ2 = 475 kg/h
  4. 4. ṁ2 = 400 kg/h
  5. 5. P = 66.67 kg/h
  6. 6. P = 1296 kg/h

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