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 1400 kg/h · 15% NaOHStream 2400 kg/h · 35% NaOHStream 3ṁ₃ = ? kg/h

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

ṁ1 = 400 kg/hx1 = 15 %ṁ2 = 400 kg/hx2 = 35 %
ṁ3 = kg/h
2.Easy
MixerStream 1300 kg/h · 30% NaOHStream 2600 kg/h · 25% NaOHStream 3x₃ = ? %

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

ṁ1 = 300 kg/hx1 = 30 %ṁ2 = 600 kg/hx2 = 25 %
x3 = %
3.Medium
MixerStream 1750 kg/h · 30% NaOHStream 2ṁ₂ = ? · 15% 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 = 750 kg/hx1 = 30 %x2 = 15 %x3 = 25 %
ṁ2 = kg/h
4.Medium
MixerStream 11000 kg/h · 35% sugarStream 2ṁ₂ = ? · 10% sugarProduct20% sugar

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

ṁ1 = 1000 kg/hx1 = 35 %x2 = 10 %x3 = 20 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F4400 kg/h · 12% NaOHProduct PP = ? · 55%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 = 4400 kg/hxF = 12 %xP = 55 %
P = kg/h
6.Hard
EvaporatorFeed F5000 kg/h · 11% saltProduct PP = ? · 45%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 = 5000 kg/hxF = 11 %xP = 45 %
P = kg/h

Answer key

  1. 1. ṁ3 = 800 kg/h
  2. 2. x3 = 26.67 %
  3. 3. ṁ2 = 375 kg/h
  4. 4. ṁ2 = 1500 kg/h
  5. 5. P = 960 kg/h
  6. 6. P = 1222 kg/h

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