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 · 15% sugarStream 2150 kg/h · 25% sugarStream 3x₃ = ? %

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

ṁ1 = 150 kg/hx1 = 15 %ṁ2 = 150 kg/hx2 = 25 %
x3 = %
2.Easy
MixerStream 1300 kg/h · 40% NaOHStream 2550 kg/h · 15% NaOHStream 3ṁ₃ = ? kg/h

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

ṁ1 = 300 kg/hx1 = 40 %ṁ2 = 550 kg/hx2 = 15 %
ṁ3 = kg/h
3.Medium
MixerStream 1950 kg/h · 45% NaOHStream 2ṁ₂ = ? · 15% NaOHProduct40% NaOH

How much of stream 2 must be added each hour to stream 1 so that the blended product contains 40% NaOH? Find ṁ2.

ṁ1 = 950 kg/hx1 = 45 %x2 = 15 %x3 = 40 %
ṁ2 = kg/h
4.Medium
MixerStream 1750 kg/h · 30% sugarStream 2ṁ₂ = ? · 20% 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 = 750 kg/hx1 = 30 %x2 = 20 %x3 = 25 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F600 kg/h · 8% saltProduct PP = ? · 30%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 = 600 kg/hxF = 8 %xP = 30 %
P = kg/h
6.Hard
EvaporatorFeed F3600 kg/h · 19% NaOHProduct P55% 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 = 3600 kg/hxF = 19 %xP = 55 %
W = kg/h

Answer key

  1. 1. x3 = 20 %
  2. 2. ṁ3 = 850 kg/h
  3. 3. ṁ2 = 190 kg/h
  4. 4. ṁ2 = 750 kg/h
  5. 5. P = 160 kg/h
  6. 6. W = 2356 kg/h

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