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 1450 kg/h · 30% saltStream 2800 kg/h · 20% saltStream 3x₃ = ? %

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

ṁ1 = 450 kg/hx1 = 30 %ṁ2 = 800 kg/hx2 = 20 %
x3 = %
2.Easy
MixerStream 11000 kg/h · 35% NaOHStream 2450 kg/h · 25% NaOHStream 3x₃ = ? %

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

ṁ1 = 1000 kg/hx1 = 35 %ṁ2 = 450 kg/hx2 = 25 %
x3 = %
3.Medium
MixerStream 1800 kg/h · 35% sugarStream 2ṁ₂ = ? · 15% sugarProduct20% sugar

How much of stream 2 must be added each hour to stream 1 so that the blended product contains 20% sugar? Find ṁ2.

ṁ1 = 800 kg/hx1 = 35 %x2 = 15 %x3 = 20 %
ṁ2 = kg/h
4.Medium
MixerStream 1800 kg/h · 50% saltStream 2ṁ₂ = ? · 5% 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 = 800 kg/hx1 = 50 %x2 = 5 %x3 = 25 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F3500 kg/h · 20% saltProduct PP = ? · 60%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 = 3500 kg/hxF = 20 %xP = 60 %
P = kg/h
6.Hard
EvaporatorFeed F1300 kg/h · 19% 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 = 1300 kg/hxF = 19 %xP = 60 %
P = kg/h

Answer key

  1. 1. x3 = 23.6 %
  2. 2. x3 = 31.9 %
  3. 3. ṁ2 = 2400 kg/h
  4. 4. ṁ2 = 1000 kg/h
  5. 5. P = 1167 kg/h
  6. 6. P = 411.7 kg/h

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