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 1750 kg/h · 30% sugarStream 2700 kg/h · 35% sugarStream 3x₃ = ? %

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

ṁ1 = 750 kg/hx1 = 30 %ṁ2 = 700 kg/hx2 = 35 %
x3 = %
2.Easy
MixerStream 1200 kg/h · 35% saltStream 2750 kg/h · 5% saltStream 3x₃ = ? %

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

ṁ1 = 200 kg/hx1 = 35 %ṁ2 = 750 kg/hx2 = 5 %
x3 = %
3.Medium
MixerStream 11000 kg/h · 35% NaOHStream 2ṁ₂ = ? · 10% NaOHProduct15% NaOH

How much of stream 2 must be added each hour to stream 1 so that the blended product contains 15% NaOH? Find ṁ2.

ṁ1 = 1000 kg/hx1 = 35 %x2 = 10 %x3 = 15 %
ṁ2 = kg/h
4.Medium
MixerStream 1650 kg/h · 15% sugarStream 2ṁ₂ = ? · 45% sugarProduct35% sugar

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

ṁ1 = 650 kg/hx1 = 15 %x2 = 45 %x3 = 35 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F900 kg/h · 17% NaOHProduct PP = ? · 30%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 = 900 kg/hxF = 17 %xP = 30 %
P = kg/h
6.Hard
EvaporatorFeed F600 kg/h · 6% sugarProduct P35% sugarVapour W (pure water)W = ? kg/h

An evaporator concentrates a sugar solution by boiling off pure water. Find the water evaporated W in kg/h.

F = 600 kg/hxF = 6 %xP = 35 %
W = kg/h

Answer key

  1. 1. x3 = 32.41 %
  2. 2. x3 = 11.32 %
  3. 3. ṁ2 = 4000 kg/h
  4. 4. ṁ2 = 1300 kg/h
  5. 5. P = 510 kg/h
  6. 6. W = 497.1 kg/h

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