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 1400 kg/h · 25% NaOHStream 2500 kg/h · 20% NaOHStream 3x₃ = ? %

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

ṁ1 = 400 kg/hx1 = 25 %ṁ2 = 500 kg/hx2 = 20 %
x3 = %
2.Easy
MixerStream 1100 kg/h · 20% sugarStream 2250 kg/h · 5% sugarStream 3ṁ₃ = ? kg/h

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

ṁ1 = 100 kg/hx1 = 20 %ṁ2 = 250 kg/hx2 = 5 %
ṁ3 = kg/h
3.Medium
MixerStream 1450 kg/h · 20% saltStream 2ṁ₂ = ? · 45% saltProduct30% salt

How much of stream 2 must be added each hour to stream 1 so that the blended product contains 30% salt? Find ṁ2.

ṁ1 = 450 kg/hx1 = 20 %x2 = 45 %x3 = 30 %
ṁ2 = kg/h
4.Medium
MixerStream 1400 kg/h · 5% saltStream 2ṁ₂ = ? · 35% saltProduct15% salt

How much of stream 2 must be added each hour to stream 1 so that the blended product contains 15% salt? Find ṁ2.

ṁ1 = 400 kg/hx1 = 5 %x2 = 35 %x3 = 15 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F3700 kg/h · 6% sugarProduct P60% 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 = 3700 kg/hxF = 6 %xP = 60 %
W = kg/h
6.Hard
EvaporatorFeed F2400 kg/h · 12% NaOHProduct PP = ? · 30%Vapour W (pure water)0% NaOH

An evaporator concentrates a NaOH solution by boiling off pure water. Find the product flow P in kg/h.

F = 2400 kg/hxF = 12 %xP = 30 %
P = kg/h

Answer key

  1. 1. x3 = 22.22 %
  2. 2. ṁ3 = 350 kg/h
  3. 3. ṁ2 = 300 kg/h
  4. 4. ṁ2 = 200 kg/h
  5. 5. W = 3330 kg/h
  6. 6. P = 960 kg/h

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