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 1550 kg/h · 5% NaOHStream 2750 kg/h · 30% NaOHStream 3x₃ = ? %

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

ṁ1 = 550 kg/hx1 = 5 %ṁ2 = 750 kg/hx2 = 30 %
x3 = %
2.Easy
MixerStream 1750 kg/h · 30% NaOHStream 2850 kg/h · 35% NaOHStream 3ṁ₃ = ? kg/h

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

ṁ1 = 750 kg/hx1 = 30 %ṁ2 = 850 kg/hx2 = 35 %
ṁ3 = kg/h
3.Medium
MixerStream 1300 kg/h · 5% saltStream 2ṁ₂ = ? · 30% saltProduct20% salt

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

ṁ1 = 300 kg/hx1 = 5 %x2 = 30 %x3 = 20 %
ṁ2 = kg/h
4.Medium
MixerStream 1700 kg/h · 45% 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 = 700 kg/hx1 = 45 %x2 = 20 %x3 = 25 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F3200 kg/h · 14% 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 = 3200 kg/hxF = 14 %xP = 30 %
P = kg/h
6.Hard
EvaporatorFeed F1000 kg/h · 11% saltProduct PP = ? · 65%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 = 1000 kg/hxF = 11 %xP = 65 %
P = kg/h

Answer key

  1. 1. x3 = 19.42 %
  2. 2. ṁ3 = 1600 kg/h
  3. 3. ṁ2 = 450 kg/h
  4. 4. ṁ2 = 2800 kg/h
  5. 5. P = 1493 kg/h
  6. 6. P = 169.2 kg/h

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