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 1400 kg/h · 15% saltStream 2800 kg/h · 5% saltStream 3x₃ = ? %

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

ṁ1 = 400 kg/hx1 = 15 %ṁ2 = 800 kg/hx2 = 5 %
x3 = %
2.Easy
MixerStream 1350 kg/h · 30% sugarStream 2700 kg/h · 25% sugarStream 3x₃ = ? %

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

ṁ1 = 350 kg/hx1 = 30 %ṁ2 = 700 kg/hx2 = 25 %
x3 = %
3.Medium
MixerStream 1800 kg/h · 10% saltStream 2ṁ₂ = ? · 45% saltProduct25% salt

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

ṁ1 = 800 kg/hx1 = 10 %x2 = 45 %x3 = 25 %
ṁ2 = kg/h
4.Medium
MixerStream 1850 kg/h · 10% NaOHStream 2ṁ₂ = ? · 30% 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 = 850 kg/hx1 = 10 %x2 = 30 %x3 = 20 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F600 kg/h · 8% sugarProduct P45% 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 = 600 kg/hxF = 8 %xP = 45 %
W = kg/h
6.Hard
EvaporatorFeed F2300 kg/h · 13% 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 = 2300 kg/hxF = 13 %xP = 50 %
W = kg/h

Answer key

  1. 1. x3 = 8.333 %
  2. 2. x3 = 26.67 %
  3. 3. ṁ2 = 600 kg/h
  4. 4. ṁ2 = 850 kg/h
  5. 5. W = 493.3 kg/h
  6. 6. W = 1702 kg/h

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