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 1950 kg/h · 25% saltStream 2950 kg/h · 35% saltStream 3ṁ₃ = ? kg/h

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

ṁ1 = 950 kg/hx1 = 25 %ṁ2 = 950 kg/hx2 = 35 %
ṁ3 = kg/h
2.Easy
MixerStream 1900 kg/h · 35% sugarStream 2200 kg/h · 20% sugarStream 3x₃ = ? %

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

ṁ1 = 900 kg/hx1 = 35 %ṁ2 = 200 kg/hx2 = 20 %
x3 = %
3.Medium
MixerStream 1950 kg/h · 10% 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 = 950 kg/hx1 = 10 %x2 = 45 %x3 = 30 %
ṁ2 = kg/h
4.Medium
MixerStream 1950 kg/h · 5% sugarStream 2ṁ₂ = ? · 35% 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 = 35 %x3 = 10 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F3900 kg/h · 15% saltProduct P65% 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 = 15 %xP = 65 %
W = kg/h
6.Hard
EvaporatorFeed F1100 kg/h · 8% NaOHProduct PP = ? · 60%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 = 1100 kg/hxF = 8 %xP = 60 %
P = kg/h

Answer key

  1. 1. ṁ3 = 1900 kg/h
  2. 2. x3 = 32.27 %
  3. 3. ṁ2 = 1267 kg/h
  4. 4. ṁ2 = 190 kg/h
  5. 5. W = 3000 kg/h
  6. 6. P = 146.7 kg/h

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