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 1900 kg/h · 10% sugarStream 2800 kg/h · 15% sugarStream 3x₃ = ? %

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

ṁ1 = 900 kg/hx1 = 10 %ṁ2 = 800 kg/hx2 = 15 %
x3 = %
2.Easy
MixerStream 1950 kg/h · 10% saltStream 2600 kg/h · 15% saltStream 3x₃ = ? %

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

ṁ1 = 950 kg/hx1 = 10 %ṁ2 = 600 kg/hx2 = 15 %
x3 = %
3.Medium
MixerStream 1400 kg/h · 15% NaOHStream 2ṁ₂ = ? · 40% 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 = 400 kg/hx1 = 15 %x2 = 40 %x3 = 35 %
ṁ2 = kg/h
4.Medium
MixerStream 1950 kg/h · 45% 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 = 950 kg/hx1 = 45 %x2 = 10 %x3 = 15 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F1500 kg/h · 9% saltProduct PP = ? · 40%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 = 1500 kg/hxF = 9 %xP = 40 %
P = kg/h
6.Hard
EvaporatorFeed F3400 kg/h · 12% saltProduct P50% 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 = 3400 kg/hxF = 12 %xP = 50 %
W = kg/h

Answer key

  1. 1. x3 = 12.35 %
  2. 2. x3 = 11.94 %
  3. 3. ṁ2 = 1600 kg/h
  4. 4. ṁ2 = 5700 kg/h
  5. 5. P = 337.5 kg/h
  6. 6. W = 2584 kg/h

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