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 1150 kg/h · 25% sugarStream 2400 kg/h · 30% sugarStream 3x₃ = ? %

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

ṁ1 = 150 kg/hx1 = 25 %ṁ2 = 400 kg/hx2 = 30 %
x3 = %
2.Easy
MixerStream 1750 kg/h · 30% saltStream 2550 kg/h · 15% saltStream 3x₃ = ? %

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

ṁ1 = 750 kg/hx1 = 30 %ṁ2 = 550 kg/hx2 = 15 %
x3 = %
3.Medium
MixerStream 1700 kg/h · 30% sugarStream 2ṁ₂ = ? · 15% sugarProduct25% sugar

How much of stream 2 must be added each hour to stream 1 so that the blended product contains 25% sugar? Find ṁ2.

ṁ1 = 700 kg/hx1 = 30 %x2 = 15 %x3 = 25 %
ṁ2 = kg/h
4.Medium
MixerStream 11000 kg/h · 30% NaOHStream 2ṁ₂ = ? · 20% 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 = 1000 kg/hx1 = 30 %x2 = 20 %x3 = 25 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F3400 kg/h · 14% NaOHProduct P30% 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 = 3400 kg/hxF = 14 %xP = 30 %
W = kg/h
6.Hard
EvaporatorFeed F2200 kg/h · 18% saltProduct P50% 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 = 2200 kg/hxF = 18 %xP = 50 %
W = kg/h

Answer key

  1. 1. x3 = 28.64 %
  2. 2. x3 = 23.65 %
  3. 3. ṁ2 = 350 kg/h
  4. 4. ṁ2 = 1000 kg/h
  5. 5. W = 1813 kg/h
  6. 6. W = 1408 kg/h

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