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 · 20% sugarStream 2250 kg/h · 25% sugarStream 3x₃ = ? %

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

ṁ1 = 300 kg/hx1 = 20 %ṁ2 = 250 kg/hx2 = 25 %
x3 = %
2.Easy
MixerStream 1550 kg/h · 15% saltStream 2950 kg/h · 10% saltStream 3ṁ₃ = ? kg/h

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

ṁ1 = 550 kg/hx1 = 15 %ṁ2 = 950 kg/hx2 = 10 %
ṁ3 = kg/h
3.Medium
MixerStream 1800 kg/h · 50% 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 = 800 kg/hx1 = 50 %x2 = 15 %x3 = 20 %
ṁ2 = kg/h
4.Medium
MixerStream 1250 kg/h · 10% sugarStream 2ṁ₂ = ? · 35% sugarProduct25% sugar

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

ṁ1 = 250 kg/hx1 = 10 %x2 = 35 %x3 = 25 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F1500 kg/h · 12% NaOHProduct P30% 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 = 1500 kg/hxF = 12 %xP = 30 %
W = kg/h
6.Hard
EvaporatorFeed F4000 kg/h · 13% NaOHProduct PP = ? · 30%Vapour W (pure water)0% NaOH

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

F = 4000 kg/hxF = 13 %xP = 30 %
P = kg/h

Answer key

  1. 1. x3 = 22.27 %
  2. 2. ṁ3 = 1500 kg/h
  3. 3. ṁ2 = 4800 kg/h
  4. 4. ṁ2 = 375 kg/h
  5. 5. W = 900 kg/h
  6. 6. P = 1733 kg/h

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