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 11000 kg/h · 10% saltStream 2150 kg/h · 5% saltStream 3x₃ = ? %

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

ṁ1 = 1000 kg/hx1 = 10 %ṁ2 = 150 kg/hx2 = 5 %
x3 = %
2.Easy
MixerStream 1350 kg/h · 10% sugarStream 2500 kg/h · 15% sugarStream 3x₃ = ? %

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

ṁ1 = 350 kg/hx1 = 10 %ṁ2 = 500 kg/hx2 = 15 %
x3 = %
3.Medium
MixerStream 1500 kg/h · 10% NaOHStream 2ṁ₂ = ? · 40% NaOHProduct20% NaOH

How much of stream 2 must be added each hour to stream 1 so that the blended product contains 20% NaOH? Find ṁ2.

ṁ1 = 500 kg/hx1 = 10 %x2 = 40 %x3 = 20 %
ṁ2 = kg/h
4.Medium
MixerStream 1700 kg/h · 20% saltStream 2ṁ₂ = ? · 45% saltProduct30% salt

How much of stream 2 must be added each hour to stream 1 so that the blended product contains 30% salt? Find ṁ2.

ṁ1 = 700 kg/hx1 = 20 %x2 = 45 %x3 = 30 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F1800 kg/h · 19% sugarProduct PP = ? · 45%Vapour W (pure water)0% sugar

An evaporator concentrates a sugar solution by boiling off pure water. Find the product flow P in kg/h.

F = 1800 kg/hxF = 19 %xP = 45 %
P = kg/h
6.Hard
EvaporatorFeed F2200 kg/h · 16% saltProduct P30% 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 = 16 %xP = 30 %
W = kg/h

Answer key

  1. 1. x3 = 9.348 %
  2. 2. x3 = 12.94 %
  3. 3. ṁ2 = 250 kg/h
  4. 4. ṁ2 = 466.7 kg/h
  5. 5. P = 760 kg/h
  6. 6. W = 1027 kg/h

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