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 1100 kg/h · 35% NaOHStream 2750 kg/h · 30% NaOHStream 3ṁ₃ = ? kg/h

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

ṁ1 = 100 kg/hx1 = 35 %ṁ2 = 750 kg/hx2 = 30 %
ṁ3 = kg/h
2.Easy
MixerStream 1900 kg/h · 40% NaOHStream 2600 kg/h · 20% NaOHStream 3x₃ = ? %

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

ṁ1 = 900 kg/hx1 = 40 %ṁ2 = 600 kg/hx2 = 20 %
x3 = %
3.Medium
MixerStream 1300 kg/h · 50% saltStream 2ṁ₂ = ? · 15% 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 = 50 %x2 = 15 %x3 = 20 %
ṁ2 = kg/h
4.Medium
MixerStream 11000 kg/h · 15% NaOHStream 2ṁ₂ = ? · 40% NaOHProduct30% NaOH

How much of stream 2 must be added each hour to stream 1 so that the blended product contains 30% NaOH? Find ṁ2.

ṁ1 = 1000 kg/hx1 = 15 %x2 = 40 %x3 = 30 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F3400 kg/h · 13% saltProduct PP = ? · 40%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 = 3400 kg/hxF = 13 %xP = 40 %
P = kg/h
6.Hard
EvaporatorFeed F1400 kg/h · 19% NaOHProduct PP = ? · 45%Vapour W (pure water)0% NaOH

An evaporator concentrates a NaOH solution by boiling off pure water. Find the product flow P in kg/h.

F = 1400 kg/hxF = 19 %xP = 45 %
P = kg/h

Answer key

  1. 1. ṁ3 = 850 kg/h
  2. 2. x3 = 32 %
  3. 3. ṁ2 = 1800 kg/h
  4. 4. ṁ2 = 1500 kg/h
  5. 5. P = 1105 kg/h
  6. 6. P = 591.1 kg/h

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