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 1700 kg/h · 30% sugarStream 2350 kg/h · 20% sugarStream 3x₃ = ? %

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

ṁ1 = 700 kg/hx1 = 30 %ṁ2 = 350 kg/hx2 = 20 %
x3 = %
2.Easy
MixerStream 1850 kg/h · 20% sugarStream 2450 kg/h · 25% sugarStream 3ṁ₃ = ? kg/h

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

ṁ1 = 850 kg/hx1 = 20 %ṁ2 = 450 kg/hx2 = 25 %
ṁ3 = kg/h
3.Medium
MixerStream 1550 kg/h · 5% saltStream 2ṁ₂ = ? · 35% 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 = 550 kg/hx1 = 5 %x2 = 35 %x3 = 30 %
ṁ2 = kg/h
4.Medium
MixerStream 1400 kg/h · 40% NaOHStream 2ṁ₂ = ? · 10% NaOHProduct15% NaOH

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

ṁ1 = 400 kg/hx1 = 40 %x2 = 10 %x3 = 15 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F2900 kg/h · 15% NaOHProduct PP = ? · 45%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 = 2900 kg/hxF = 15 %xP = 45 %
P = kg/h
6.Hard
EvaporatorFeed F3700 kg/h · 11% NaOHProduct P40% NaOHVapour W (pure water)W = ? kg/h

An evaporator concentrates a NaOH solution by boiling off pure water. Find the water evaporated W in kg/h.

F = 3700 kg/hxF = 11 %xP = 40 %
W = kg/h

Answer key

  1. 1. x3 = 26.67 %
  2. 2. ṁ3 = 1300 kg/h
  3. 3. ṁ2 = 2750 kg/h
  4. 4. ṁ2 = 2000 kg/h
  5. 5. P = 966.7 kg/h
  6. 6. W = 2683 kg/h

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