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 · 30% NaOHStream 2750 kg/h · 35% NaOHStream 3x₃ = ? %

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

ṁ1 = 500 kg/hx1 = 30 %ṁ2 = 750 kg/hx2 = 35 %
x3 = %
2.Easy
MixerStream 1950 kg/h · 35% NaOHStream 2150 kg/h · 15% NaOHStream 3ṁ₃ = ? kg/h

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

ṁ1 = 950 kg/hx1 = 35 %ṁ2 = 150 kg/hx2 = 15 %
ṁ3 = kg/h
3.Medium
MixerStream 1700 kg/h · 30% sugarStream 2ṁ₂ = ? · 5% 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 = 700 kg/hx1 = 30 %x2 = 5 %x3 = 15 %
ṁ2 = kg/h
4.Medium
MixerStream 1500 kg/h · 15% sugarStream 2ṁ₂ = ? · 30% sugarProduct20% sugar

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

ṁ1 = 500 kg/hx1 = 15 %x2 = 30 %x3 = 20 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F4600 kg/h · 11% NaOHProduct PP = ? · 40%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 = 4600 kg/hxF = 11 %xP = 40 %
P = kg/h
6.Hard
EvaporatorFeed F500 kg/h · 14% sugarProduct PP = ? · 30%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 = 500 kg/hxF = 14 %xP = 30 %
P = kg/h

Answer key

  1. 1. x3 = 33 %
  2. 2. ṁ3 = 1100 kg/h
  3. 3. ṁ2 = 1050 kg/h
  4. 4. ṁ2 = 250 kg/h
  5. 5. P = 1265 kg/h
  6. 6. P = 233.3 kg/h

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