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 · 10% NaOHStream 2650 kg/h · 20% NaOHStream 3x₃ = ? %

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

ṁ1 = 650 kg/hx1 = 10 %ṁ2 = 650 kg/hx2 = 20 %
x3 = %
2.Easy
MixerStream 1600 kg/h · 10% saltStream 2300 kg/h · 25% saltStream 3x₃ = ? %

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

ṁ1 = 600 kg/hx1 = 10 %ṁ2 = 300 kg/hx2 = 25 %
x3 = %
3.Medium
MixerStream 1250 kg/h · 45% NaOHStream 2ṁ₂ = ? · 5% NaOHProduct35% NaOH

How much of stream 2 must be added each hour to stream 1 so that the blended product contains 35% NaOH? Find ṁ2.

ṁ1 = 250 kg/hx1 = 45 %x2 = 5 %x3 = 35 %
ṁ2 = kg/h
4.Medium
MixerStream 1900 kg/h · 5% NaOHStream 2ṁ₂ = ? · 30% 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 = 900 kg/hx1 = 5 %x2 = 30 %x3 = 25 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F3700 kg/h · 15% sugarProduct PP = ? · 55%Vapour W (pure water)0% sugar

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

F = 3700 kg/hxF = 15 %xP = 55 %
P = kg/h
6.Hard
EvaporatorFeed F4100 kg/h · 7% saltProduct PP = ? · 65%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 = 4100 kg/hxF = 7 %xP = 65 %
P = kg/h

Answer key

  1. 1. x3 = 15 %
  2. 2. x3 = 15 %
  3. 3. ṁ2 = 83.33 kg/h
  4. 4. ṁ2 = 3600 kg/h
  5. 5. P = 1009 kg/h
  6. 6. P = 441.5 kg/h

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