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 1300 kg/h · 10% NaOHStream 2500 kg/h · 30% NaOHStream 3ṁ₃ = ? kg/h

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

ṁ1 = 300 kg/hx1 = 10 %ṁ2 = 500 kg/hx2 = 30 %
ṁ3 = kg/h
2.Easy
MixerStream 1100 kg/h · 5% saltStream 2750 kg/h · 40% saltStream 3x₃ = ? %

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

ṁ1 = 100 kg/hx1 = 5 %ṁ2 = 750 kg/hx2 = 40 %
x3 = %
3.Medium
MixerStream 1250 kg/h · 15% 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 = 250 kg/hx1 = 15 %x2 = 30 %x3 = 25 %
ṁ2 = kg/h
4.Medium
MixerStream 1900 kg/h · 50% NaOHStream 2ṁ₂ = ? · 5% NaOHProduct45% NaOH

How much of stream 2 must be added each hour to stream 1 so that the blended product contains 45% NaOH? Find ṁ2.

ṁ1 = 900 kg/hx1 = 50 %x2 = 5 %x3 = 45 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F700 kg/h · 14% 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 = 700 kg/hxF = 14 %xP = 50 %
W = kg/h
6.Hard
EvaporatorFeed F1400 kg/h · 13% 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 = 1400 kg/hxF = 13 %xP = 45 %
W = kg/h

Answer key

  1. 1. ṁ3 = 800 kg/h
  2. 2. x3 = 35.88 %
  3. 3. ṁ2 = 500 kg/h
  4. 4. ṁ2 = 112.5 kg/h
  5. 5. W = 504 kg/h
  6. 6. W = 995.6 kg/h

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