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 1500 kg/h · 20% sugarStream 2400 kg/h · 25% sugarStream 3x₃ = ? %

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

ṁ1 = 500 kg/hx1 = 20 %ṁ2 = 400 kg/hx2 = 25 %
x3 = %
2.Easy
MixerStream 1600 kg/h · 35% saltStream 2250 kg/h · 25% saltStream 3ṁ₃ = ? kg/h

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

ṁ1 = 600 kg/hx1 = 35 %ṁ2 = 250 kg/hx2 = 25 %
ṁ3 = kg/h
3.Medium
MixerStream 1350 kg/h · 45% saltStream 2ṁ₂ = ? · 20% 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 = 350 kg/hx1 = 45 %x2 = 20 %x3 = 35 %
ṁ2 = kg/h
4.Medium
MixerStream 1450 kg/h · 5% sugarStream 2ṁ₂ = ? · 40% sugarProduct10% sugar

How much of stream 2 must be added each hour to stream 1 so that the blended product contains 10% sugar? Find ṁ2.

ṁ1 = 450 kg/hx1 = 5 %x2 = 40 %x3 = 10 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F3200 kg/h · 12% saltProduct PP = ? · 65%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 = 3200 kg/hxF = 12 %xP = 65 %
P = kg/h
6.Hard
EvaporatorFeed F3800 kg/h · 11% saltProduct P40% 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 = 3800 kg/hxF = 11 %xP = 40 %
W = kg/h

Answer key

  1. 1. x3 = 22.22 %
  2. 2. ṁ3 = 850 kg/h
  3. 3. ṁ2 = 233.3 kg/h
  4. 4. ṁ2 = 75 kg/h
  5. 5. P = 590.8 kg/h
  6. 6. W = 2755 kg/h

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