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 1700 kg/h · 5% saltStream 21000 kg/h · 25% saltStream 3ṁ₃ = ? kg/h

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

ṁ1 = 700 kg/hx1 = 5 %ṁ2 = 1000 kg/hx2 = 25 %
ṁ3 = kg/h
2.Easy
MixerStream 1800 kg/h · 30% NaOHStream 2950 kg/h · 5% NaOHStream 3x₃ = ? %

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

ṁ1 = 800 kg/hx1 = 30 %ṁ2 = 950 kg/hx2 = 5 %
x3 = %
3.Medium
MixerStream 1800 kg/h · 5% NaOHStream 2ṁ₂ = ? · 35% 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 = 800 kg/hx1 = 5 %x2 = 35 %x3 = 20 %
ṁ2 = kg/h
4.Medium
MixerStream 11000 kg/h · 5% saltStream 2ṁ₂ = ? · 45% 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 = 1000 kg/hx1 = 5 %x2 = 45 %x3 = 20 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F4300 kg/h · 10% NaOHProduct P40% 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 = 4300 kg/hxF = 10 %xP = 40 %
W = kg/h
6.Hard
EvaporatorFeed F3700 kg/h · 12% sugarProduct PP = ? · 65%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 = 12 %xP = 65 %
P = kg/h

Answer key

  1. 1. ṁ3 = 1700 kg/h
  2. 2. x3 = 16.43 %
  3. 3. ṁ2 = 800 kg/h
  4. 4. ṁ2 = 600 kg/h
  5. 5. W = 3225 kg/h
  6. 6. P = 683.1 kg/h

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