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 1800 kg/h · 30% sugarStream 2250 kg/h · 15% sugarStream 3ṁ₃ = ? kg/h

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

ṁ1 = 800 kg/hx1 = 30 %ṁ2 = 250 kg/hx2 = 15 %
ṁ3 = kg/h
2.Easy
MixerStream 1900 kg/h · 40% saltStream 2650 kg/h · 5% saltStream 3x₃ = ? %

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

ṁ1 = 900 kg/hx1 = 40 %ṁ2 = 650 kg/hx2 = 5 %
x3 = %
3.Medium
MixerStream 11000 kg/h · 20% NaOHStream 2ṁ₂ = ? · 50% NaOHProduct25% NaOH

How much of stream 2 must be added each hour to stream 1 so that the blended product contains 25% NaOH? Find ṁ2.

ṁ1 = 1000 kg/hx1 = 20 %x2 = 50 %x3 = 25 %
ṁ2 = kg/h
4.Medium
MixerStream 1650 kg/h · 10% NaOHStream 2ṁ₂ = ? · 30% 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 = 650 kg/hx1 = 10 %x2 = 30 %x3 = 20 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F2300 kg/h · 20% sugarProduct P65% 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 = 2300 kg/hxF = 20 %xP = 65 %
W = kg/h
6.Hard
EvaporatorFeed F3100 kg/h · 8% saltProduct PP = ? · 50%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 = 3100 kg/hxF = 8 %xP = 50 %
P = kg/h

Answer key

  1. 1. ṁ3 = 1050 kg/h
  2. 2. x3 = 25.32 %
  3. 3. ṁ2 = 200 kg/h
  4. 4. ṁ2 = 650 kg/h
  5. 5. W = 1592 kg/h
  6. 6. P = 496 kg/h

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