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 1950 kg/h · 5% saltStream 2100 kg/h · 35% saltStream 3x₃ = ? %

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

ṁ1 = 950 kg/hx1 = 5 %ṁ2 = 100 kg/hx2 = 35 %
x3 = %
2.Easy
MixerStream 1350 kg/h · 25% saltStream 2950 kg/h · 40% saltStream 3ṁ₃ = ? kg/h

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

ṁ1 = 350 kg/hx1 = 25 %ṁ2 = 950 kg/hx2 = 40 %
ṁ3 = kg/h
3.Medium
MixerStream 1450 kg/h · 50% 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 = 450 kg/hx1 = 50 %x2 = 5 %x3 = 25 %
ṁ2 = kg/h
4.Medium
MixerStream 1600 kg/h · 30% 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 = 600 kg/hx1 = 30 %x2 = 5 %x3 = 25 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F3300 kg/h · 5% 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 = 3300 kg/hxF = 5 %xP = 60 %
P = kg/h
6.Hard
EvaporatorFeed F4200 kg/h · 13% 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 = 4200 kg/hxF = 13 %xP = 65 %
W = kg/h

Answer key

  1. 1. x3 = 7.857 %
  2. 2. ṁ3 = 1300 kg/h
  3. 3. ṁ2 = 562.5 kg/h
  4. 4. ṁ2 = 150 kg/h
  5. 5. P = 275 kg/h
  6. 6. W = 3360 kg/h

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