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 · 15% saltStream 2450 kg/h · 25% saltStream 3ṁ₃ = ? kg/h

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

ṁ1 = 950 kg/hx1 = 15 %ṁ2 = 450 kg/hx2 = 25 %
ṁ3 = kg/h
2.Easy
MixerStream 1450 kg/h · 35% sugarStream 2100 kg/h · 25% sugarStream 3x₃ = ? %

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

ṁ1 = 450 kg/hx1 = 35 %ṁ2 = 100 kg/hx2 = 25 %
x3 = %
3.Medium
MixerStream 1600 kg/h · 35% saltStream 2ṁ₂ = ? · 5% 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 = 600 kg/hx1 = 35 %x2 = 5 %x3 = 25 %
ṁ2 = kg/h
4.Medium
MixerStream 1800 kg/h · 40% saltStream 2ṁ₂ = ? · 5% saltProduct20% salt

How much of stream 2 must be added each hour to stream 1 so that the blended product contains 20% salt? Find ṁ2.

ṁ1 = 800 kg/hx1 = 40 %x2 = 5 %x3 = 20 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F3900 kg/h · 15% NaOHProduct P50% 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 = 3900 kg/hxF = 15 %xP = 50 %
W = kg/h
6.Hard
EvaporatorFeed F4000 kg/h · 18% sugarProduct PP = ? · 45%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 = 4000 kg/hxF = 18 %xP = 45 %
P = kg/h

Answer key

  1. 1. ṁ3 = 1400 kg/h
  2. 2. x3 = 33.18 %
  3. 3. ṁ2 = 300 kg/h
  4. 4. ṁ2 = 1067 kg/h
  5. 5. W = 2730 kg/h
  6. 6. P = 1600 kg/h

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