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 1500 kg/h · 40% NaOHStream 2100 kg/h · 20% NaOHStream 3ṁ₃ = ? kg/h

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

ṁ1 = 500 kg/hx1 = 40 %ṁ2 = 100 kg/hx2 = 20 %
ṁ3 = kg/h
2.Easy
MixerStream 1150 kg/h · 10% NaOHStream 2250 kg/h · 25% NaOHStream 3x₃ = ? %

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

ṁ1 = 150 kg/hx1 = 10 %ṁ2 = 250 kg/hx2 = 25 %
x3 = %
3.Medium
MixerStream 1850 kg/h · 20% saltStream 2ṁ₂ = ? · 35% 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 = 850 kg/hx1 = 20 %x2 = 35 %x3 = 25 %
ṁ2 = kg/h
4.Medium
MixerStream 1500 kg/h · 40% NaOHStream 2ṁ₂ = ? · 5% 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 = 40 %x2 = 5 %x3 = 20 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F3700 kg/h · 14% sugarProduct PP = ? · 55%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 = 3700 kg/hxF = 14 %xP = 55 %
P = kg/h
6.Hard
EvaporatorFeed F1200 kg/h · 6% NaOHProduct P65% NaOHVapour W (pure water)W = ? kg/h

An evaporator concentrates a NaOH solution by boiling off pure water. Find the water evaporated W in kg/h.

F = 1200 kg/hxF = 6 %xP = 65 %
W = kg/h

Answer key

  1. 1. ṁ3 = 600 kg/h
  2. 2. x3 = 19.38 %
  3. 3. ṁ2 = 425 kg/h
  4. 4. ṁ2 = 666.7 kg/h
  5. 5. P = 941.8 kg/h
  6. 6. W = 1089 kg/h

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