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 · 35% saltStream 2250 kg/h · 10% saltStream 3x₃ = ? %

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

ṁ1 = 750 kg/hx1 = 35 %ṁ2 = 250 kg/hx2 = 10 %
x3 = %
2.Easy
MixerStream 1500 kg/h · 5% sugarStream 2700 kg/h · 10% sugarStream 3x₃ = ? %

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

ṁ1 = 500 kg/hx1 = 5 %ṁ2 = 700 kg/hx2 = 10 %
x3 = %
3.Medium
MixerStream 1900 kg/h · 35% 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 = 900 kg/hx1 = 35 %x2 = 15 %x3 = 25 %
ṁ2 = kg/h
4.Medium
MixerStream 1950 kg/h · 20% saltStream 2ṁ₂ = ? · 45% saltProduct35% salt

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

ṁ1 = 950 kg/hx1 = 20 %x2 = 45 %x3 = 35 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F3000 kg/h · 19% NaOHProduct P45% 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 = 3000 kg/hxF = 19 %xP = 45 %
W = kg/h
6.Hard
EvaporatorFeed F1500 kg/h · 10% saltProduct P40% saltVapour W (pure water)W = ? kg/h

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

F = 1500 kg/hxF = 10 %xP = 40 %
W = kg/h

Answer key

  1. 1. x3 = 28.75 %
  2. 2. x3 = 7.917 %
  3. 3. ṁ2 = 900 kg/h
  4. 4. ṁ2 = 1425 kg/h
  5. 5. W = 1733 kg/h
  6. 6. W = 1125 kg/h

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