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 1350 kg/h · 35% saltStream 2900 kg/h · 5% saltStream 3ṁ₃ = ? kg/h

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

ṁ1 = 350 kg/hx1 = 35 %ṁ2 = 900 kg/hx2 = 5 %
ṁ3 = kg/h
2.Easy
MixerStream 1600 kg/h · 30% saltStream 2750 kg/h · 40% saltStream 3x₃ = ? %

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

ṁ1 = 600 kg/hx1 = 30 %ṁ2 = 750 kg/hx2 = 40 %
x3 = %
3.Medium
MixerStream 11000 kg/h · 35% NaOHStream 2ṁ₂ = ? · 15% NaOHProduct20% NaOH

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

ṁ1 = 1000 kg/hx1 = 35 %x2 = 15 %x3 = 20 %
ṁ2 = kg/h
4.Medium
MixerStream 1450 kg/h · 45% saltStream 2ṁ₂ = ? · 10% 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 = 450 kg/hx1 = 45 %x2 = 10 %x3 = 35 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F3700 kg/h · 18% sugarProduct P45% 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 = 3700 kg/hxF = 18 %xP = 45 %
W = kg/h
6.Hard
EvaporatorFeed F1400 kg/h · 7% sugarProduct PP = ? · 45%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 = 1400 kg/hxF = 7 %xP = 45 %
P = kg/h

Answer key

  1. 1. ṁ3 = 1250 kg/h
  2. 2. x3 = 35.56 %
  3. 3. ṁ2 = 3000 kg/h
  4. 4. ṁ2 = 180 kg/h
  5. 5. W = 2220 kg/h
  6. 6. P = 217.8 kg/h

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