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% NaOHStream 2400 kg/h · 10% NaOHStream 3ṁ₃ = ? kg/h

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

ṁ1 = 350 kg/hx1 = 35 %ṁ2 = 400 kg/hx2 = 10 %
ṁ3 = kg/h
2.Easy
MixerStream 1250 kg/h · 15% sugarStream 2700 kg/h · 30% sugarStream 3ṁ₃ = ? kg/h

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

ṁ1 = 250 kg/hx1 = 15 %ṁ2 = 700 kg/hx2 = 30 %
ṁ3 = kg/h
3.Medium
MixerStream 1300 kg/h · 35% saltStream 2ṁ₂ = ? · 5% saltProduct15% salt

How much of stream 2 must be added each hour to stream 1 so that the blended product contains 15% salt? Find ṁ2.

ṁ1 = 300 kg/hx1 = 35 %x2 = 5 %x3 = 15 %
ṁ2 = kg/h
4.Medium
MixerStream 1300 kg/h · 10% NaOHStream 2ṁ₂ = ? · 40% 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 = 300 kg/hx1 = 10 %x2 = 40 %x3 = 25 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F1900 kg/h · 20% saltProduct P35% saltVapour W (pure water)W = ? kg/h

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

F = 1900 kg/hxF = 20 %xP = 35 %
W = kg/h
6.Hard
EvaporatorFeed F2400 kg/h · 6% NaOHProduct P35% 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 = 2400 kg/hxF = 6 %xP = 35 %
W = kg/h

Answer key

  1. 1. ṁ3 = 750 kg/h
  2. 2. ṁ3 = 950 kg/h
  3. 3. ṁ2 = 600 kg/h
  4. 4. ṁ2 = 300 kg/h
  5. 5. W = 814.3 kg/h
  6. 6. W = 1989 kg/h

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