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 1600 kg/h · 25% NaOHStream 2500 kg/h · 35% NaOHStream 3x₃ = ? %

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

ṁ1 = 600 kg/hx1 = 25 %ṁ2 = 500 kg/hx2 = 35 %
x3 = %
2.Easy
MixerStream 1700 kg/h · 5% sugarStream 2650 kg/h · 25% sugarStream 3x₃ = ? %

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

ṁ1 = 700 kg/hx1 = 5 %ṁ2 = 650 kg/hx2 = 25 %
x3 = %
3.Medium
MixerStream 1500 kg/h · 20% saltStream 2ṁ₂ = ? · 30% saltProduct25% salt

How much of stream 2 must be added each hour to stream 1 so that the blended product contains 25% salt? Find ṁ2.

ṁ1 = 500 kg/hx1 = 20 %x2 = 30 %x3 = 25 %
ṁ2 = kg/h
4.Medium
MixerStream 1950 kg/h · 5% sugarStream 2ṁ₂ = ? · 45% 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 = 950 kg/hx1 = 5 %x2 = 45 %x3 = 10 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F1900 kg/h · 13% sugarProduct PP = ? · 40%Vapour W (pure water)0% sugar

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

F = 1900 kg/hxF = 13 %xP = 40 %
P = kg/h
6.Hard
EvaporatorFeed F1200 kg/h · 17% saltProduct P45% 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 = 1200 kg/hxF = 17 %xP = 45 %
W = kg/h

Answer key

  1. 1. x3 = 29.55 %
  2. 2. x3 = 14.63 %
  3. 3. ṁ2 = 500 kg/h
  4. 4. ṁ2 = 135.7 kg/h
  5. 5. P = 617.5 kg/h
  6. 6. W = 746.7 kg/h

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