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 1350 kg/h · 20% saltStream 2650 kg/h · 10% saltStream 3ṁ₃ = ? kg/h

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

ṁ1 = 350 kg/hx1 = 20 %ṁ2 = 650 kg/hx2 = 10 %
ṁ3 = kg/h
2.Easy
MixerStream 1850 kg/h · 25% NaOHStream 2350 kg/h · 10% NaOHStream 3ṁ₃ = ? kg/h

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

ṁ1 = 850 kg/hx1 = 25 %ṁ2 = 350 kg/hx2 = 10 %
ṁ3 = kg/h
3.Medium
MixerStream 1250 kg/h · 30% NaOHStream 2ṁ₂ = ? · 15% 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 = 250 kg/hx1 = 30 %x2 = 15 %x3 = 20 %
ṁ2 = kg/h
4.Medium
MixerStream 1550 kg/h · 10% saltStream 2ṁ₂ = ? · 50% saltProduct40% salt

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

ṁ1 = 550 kg/hx1 = 10 %x2 = 50 %x3 = 40 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F2500 kg/h · 17% saltProduct PP = ? · 45%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 = 2500 kg/hxF = 17 %xP = 45 %
P = kg/h
6.Hard
EvaporatorFeed F2500 kg/h · 15% saltProduct P65% 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 = 2500 kg/hxF = 15 %xP = 65 %
W = kg/h

Answer key

  1. 1. ṁ3 = 1000 kg/h
  2. 2. ṁ3 = 1200 kg/h
  3. 3. ṁ2 = 500 kg/h
  4. 4. ṁ2 = 1650 kg/h
  5. 5. P = 944.4 kg/h
  6. 6. W = 1923 kg/h

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