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 1550 kg/h · 20% sugarStream 2150 kg/h · 5% sugarStream 3x₃ = ? %

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

ṁ1 = 550 kg/hx1 = 20 %ṁ2 = 150 kg/hx2 = 5 %
x3 = %
2.Easy
MixerStream 1900 kg/h · 30% saltStream 2350 kg/h · 40% saltStream 3x₃ = ? %

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

ṁ1 = 900 kg/hx1 = 30 %ṁ2 = 350 kg/hx2 = 40 %
x3 = %
3.Medium
MixerStream 1250 kg/h · 10% sugarStream 2ṁ₂ = ? · 40% 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 = 250 kg/hx1 = 10 %x2 = 40 %x3 = 25 %
ṁ2 = kg/h
4.Medium
MixerStream 1750 kg/h · 5% NaOHStream 2ṁ₂ = ? · 30% 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 = 750 kg/hx1 = 5 %x2 = 30 %x3 = 25 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F5000 kg/h · 15% saltProduct PP = ? · 35%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 = 5000 kg/hxF = 15 %xP = 35 %
P = kg/h
6.Hard
EvaporatorFeed F3600 kg/h · 15% sugarProduct P50% 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 = 3600 kg/hxF = 15 %xP = 50 %
W = kg/h

Answer key

  1. 1. x3 = 16.79 %
  2. 2. x3 = 32.8 %
  3. 3. ṁ2 = 250 kg/h
  4. 4. ṁ2 = 3000 kg/h
  5. 5. P = 2143 kg/h
  6. 6. W = 2520 kg/h

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