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 1150 kg/h · 20% sugarStream 2550 kg/h · 15% sugarStream 3x₃ = ? %

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

ṁ1 = 150 kg/hx1 = 20 %ṁ2 = 550 kg/hx2 = 15 %
x3 = %
2.Easy
MixerStream 11000 kg/h · 40% NaOHStream 2950 kg/h · 30% NaOHStream 3ṁ₃ = ? kg/h

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

ṁ1 = 1000 kg/hx1 = 40 %ṁ2 = 950 kg/hx2 = 30 %
ṁ3 = kg/h
3.Medium
MixerStream 11000 kg/h · 50% sugarStream 2ṁ₂ = ? · 10% 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 = 1000 kg/hx1 = 50 %x2 = 10 %x3 = 25 %
ṁ2 = kg/h
4.Medium
MixerStream 1300 kg/h · 20% 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 = 300 kg/hx1 = 20 %x2 = 45 %x3 = 35 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F3900 kg/h · 11% saltProduct P55% 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 = 3900 kg/hxF = 11 %xP = 55 %
W = kg/h
6.Hard
EvaporatorFeed F3800 kg/h · 12% sugarProduct P30% 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 = 3800 kg/hxF = 12 %xP = 30 %
W = kg/h

Answer key

  1. 1. x3 = 16.07 %
  2. 2. ṁ3 = 1950 kg/h
  3. 3. ṁ2 = 1667 kg/h
  4. 4. ṁ2 = 450 kg/h
  5. 5. W = 3120 kg/h
  6. 6. W = 2280 kg/h

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