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 1200 kg/h · 25% saltStream 2850 kg/h · 35% saltStream 3x₃ = ? %

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

ṁ1 = 200 kg/hx1 = 25 %ṁ2 = 850 kg/hx2 = 35 %
x3 = %
2.Easy
MixerStream 1950 kg/h · 5% saltStream 2600 kg/h · 20% saltStream 3ṁ₃ = ? kg/h

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

ṁ1 = 950 kg/hx1 = 5 %ṁ2 = 600 kg/hx2 = 20 %
ṁ3 = kg/h
3.Medium
MixerStream 1950 kg/h · 45% NaOHStream 2ṁ₂ = ? · 15% NaOHProduct25% NaOH

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

ṁ1 = 950 kg/hx1 = 45 %x2 = 15 %x3 = 25 %
ṁ2 = kg/h
4.Medium
MixerStream 1450 kg/h · 50% saltStream 2ṁ₂ = ? · 10% saltProduct35% salt

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

ṁ1 = 450 kg/hx1 = 50 %x2 = 10 %x3 = 35 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F4800 kg/h · 9% sugarProduct PP = ? · 40%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 = 4800 kg/hxF = 9 %xP = 40 %
P = kg/h
6.Hard
EvaporatorFeed F1700 kg/h · 12% 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 = 1700 kg/hxF = 12 %xP = 65 %
W = kg/h

Answer key

  1. 1. x3 = 33.1 %
  2. 2. ṁ3 = 1550 kg/h
  3. 3. ṁ2 = 1900 kg/h
  4. 4. ṁ2 = 270 kg/h
  5. 5. P = 1080 kg/h
  6. 6. W = 1386 kg/h

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