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 · 35% sugarStream 2750 kg/h · 5% sugarStream 3ṁ₃ = ? kg/h

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

ṁ1 = 550 kg/hx1 = 35 %ṁ2 = 750 kg/hx2 = 5 %
ṁ3 = kg/h
2.Easy
MixerStream 1750 kg/h · 40% saltStream 2750 kg/h · 5% saltStream 3x₃ = ? %

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

ṁ1 = 750 kg/hx1 = 40 %ṁ2 = 750 kg/hx2 = 5 %
x3 = %
3.Medium
MixerStream 1500 kg/h · 5% saltStream 2ṁ₂ = ? · 50% saltProduct10% salt

How much of stream 2 must be added each hour to stream 1 so that the blended product contains 10% salt? Find ṁ2.

ṁ1 = 500 kg/hx1 = 5 %x2 = 50 %x3 = 10 %
ṁ2 = kg/h
4.Medium
MixerStream 1450 kg/h · 50% NaOHStream 2ṁ₂ = ? · 20% NaOHProduct40% NaOH

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

ṁ1 = 450 kg/hx1 = 50 %x2 = 20 %x3 = 40 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F4600 kg/h · 8% NaOHProduct P45% NaOHVapour W (pure water)W = ? kg/h

An evaporator concentrates a NaOH solution by boiling off pure water. Find the water evaporated W in kg/h.

F = 4600 kg/hxF = 8 %xP = 45 %
W = kg/h
6.Hard
EvaporatorFeed F1000 kg/h · 18% sugarProduct P60% sugarVapour W (pure water)W = ? kg/h

An evaporator concentrates a sugar solution by boiling off pure water. Find the water evaporated W in kg/h.

F = 1000 kg/hxF = 18 %xP = 60 %
W = kg/h

Answer key

  1. 1. ṁ3 = 1300 kg/h
  2. 2. x3 = 22.5 %
  3. 3. ṁ2 = 62.5 kg/h
  4. 4. ṁ2 = 225 kg/h
  5. 5. W = 3782 kg/h
  6. 6. W = 700 kg/h

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