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 1100 kg/h · 15% saltStream 2400 kg/h · 5% saltStream 3x₃ = ? %

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

ṁ1 = 100 kg/hx1 = 15 %ṁ2 = 400 kg/hx2 = 5 %
x3 = %
2.Easy
MixerStream 1350 kg/h · 10% NaOHStream 2550 kg/h · 25% NaOHStream 3ṁ₃ = ? kg/h

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

ṁ1 = 350 kg/hx1 = 10 %ṁ2 = 550 kg/hx2 = 25 %
ṁ3 = kg/h
3.Medium
MixerStream 1650 kg/h · 50% NaOHStream 2ṁ₂ = ? · 15% NaOHProduct45% NaOH

How much of stream 2 must be added each hour to stream 1 so that the blended product contains 45% NaOH? Find ṁ2.

ṁ1 = 650 kg/hx1 = 50 %x2 = 15 %x3 = 45 %
ṁ2 = kg/h
4.Medium
MixerStream 1850 kg/h · 10% NaOHStream 2ṁ₂ = ? · 50% NaOHProduct35% NaOH

How much of stream 2 must be added each hour to stream 1 so that the blended product contains 35% NaOH? Find ṁ2.

ṁ1 = 850 kg/hx1 = 10 %x2 = 50 %x3 = 35 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F900 kg/h · 15% sugarProduct PP = ? · 55%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 = 900 kg/hxF = 15 %xP = 55 %
P = kg/h
6.Hard
EvaporatorFeed F2900 kg/h · 18% NaOHProduct PP = ? · 50%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 = 2900 kg/hxF = 18 %xP = 50 %
P = kg/h

Answer key

  1. 1. x3 = 7 %
  2. 2. ṁ3 = 900 kg/h
  3. 3. ṁ2 = 108.3 kg/h
  4. 4. ṁ2 = 1417 kg/h
  5. 5. P = 245.5 kg/h
  6. 6. P = 1044 kg/h

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