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 1650 kg/h · 5% NaOHStream 2900 kg/h · 30% NaOHStream 3x₃ = ? %

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

ṁ1 = 650 kg/hx1 = 5 %ṁ2 = 900 kg/hx2 = 30 %
x3 = %
2.Easy
MixerStream 11000 kg/h · 5% sugarStream 2150 kg/h · 35% sugarStream 3ṁ₃ = ? kg/h

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

ṁ1 = 1000 kg/hx1 = 5 %ṁ2 = 150 kg/hx2 = 35 %
ṁ3 = kg/h
3.Medium
MixerStream 1400 kg/h · 35% sugarStream 2ṁ₂ = ? · 15% 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 = 400 kg/hx1 = 35 %x2 = 15 %x3 = 20 %
ṁ2 = kg/h
4.Medium
MixerStream 1700 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 = 700 kg/hx1 = 10 %x2 = 30 %x3 = 20 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F3500 kg/h · 20% 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 = 3500 kg/hxF = 20 %xP = 40 %
P = kg/h
6.Hard
EvaporatorFeed F1000 kg/h · 15% NaOHProduct PP = ? · 35%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 = 1000 kg/hxF = 15 %xP = 35 %
P = kg/h

Answer key

  1. 1. x3 = 19.52 %
  2. 2. ṁ3 = 1150 kg/h
  3. 3. ṁ2 = 1200 kg/h
  4. 4. ṁ2 = 700 kg/h
  5. 5. P = 1750 kg/h
  6. 6. P = 428.6 kg/h

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