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 1500 kg/h · 15% saltStream 2500 kg/h · 5% saltStream 3x₃ = ? %

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

ṁ1 = 500 kg/hx1 = 15 %ṁ2 = 500 kg/hx2 = 5 %
x3 = %
2.Easy
MixerStream 1850 kg/h · 25% saltStream 2850 kg/h · 15% saltStream 3ṁ₃ = ? kg/h

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

ṁ1 = 850 kg/hx1 = 25 %ṁ2 = 850 kg/hx2 = 15 %
ṁ3 = kg/h
3.Medium
MixerStream 1200 kg/h · 5% saltStream 2ṁ₂ = ? · 40% 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 = 200 kg/hx1 = 5 %x2 = 40 %x3 = 25 %
ṁ2 = kg/h
4.Medium
MixerStream 1800 kg/h · 10% sugarStream 2ṁ₂ = ? · 30% sugarProduct15% sugar

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

ṁ1 = 800 kg/hx1 = 10 %x2 = 30 %x3 = 15 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F4500 kg/h · 12% sugarProduct P35% sugarVapour W (pure water)W = ? kg/h

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

F = 4500 kg/hxF = 12 %xP = 35 %
W = kg/h
6.Hard
EvaporatorFeed F3100 kg/h · 5% NaOHProduct P30% 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 = 3100 kg/hxF = 5 %xP = 30 %
W = kg/h

Answer key

  1. 1. x3 = 10 %
  2. 2. ṁ3 = 1700 kg/h
  3. 3. ṁ2 = 266.7 kg/h
  4. 4. ṁ2 = 266.7 kg/h
  5. 5. W = 2957 kg/h
  6. 6. W = 2583 kg/h

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