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 1250 kg/h · 30% NaOHStream 2250 kg/h · 15% NaOHStream 3x₃ = ? %

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

ṁ1 = 250 kg/hx1 = 30 %ṁ2 = 250 kg/hx2 = 15 %
x3 = %
2.Easy
MixerStream 1700 kg/h · 15% sugarStream 2350 kg/h · 25% sugarStream 3ṁ₃ = ? kg/h

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

ṁ1 = 700 kg/hx1 = 15 %ṁ2 = 350 kg/hx2 = 25 %
ṁ3 = kg/h
3.Medium
MixerStream 1200 kg/h · 15% NaOHStream 2ṁ₂ = ? · 45% NaOHProduct35% NaOH

How much of stream 2 must be added each hour to stream 1 so that the blended product contains 35% NaOH? Find ṁ2.

ṁ1 = 200 kg/hx1 = 15 %x2 = 45 %x3 = 35 %
ṁ2 = kg/h
4.Medium
MixerStream 1200 kg/h · 40% sugarStream 2ṁ₂ = ? · 5% 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 = 200 kg/hx1 = 40 %x2 = 5 %x3 = 25 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F3600 kg/h · 9% sugarProduct PP = ? · 60%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 = 3600 kg/hxF = 9 %xP = 60 %
P = kg/h
6.Hard
EvaporatorFeed F4200 kg/h · 14% sugarProduct P40% 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 = 4200 kg/hxF = 14 %xP = 40 %
W = kg/h

Answer key

  1. 1. x3 = 22.5 %
  2. 2. ṁ3 = 1050 kg/h
  3. 3. ṁ2 = 400 kg/h
  4. 4. ṁ2 = 150 kg/h
  5. 5. P = 540 kg/h
  6. 6. W = 2730 kg/h

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