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 1400 kg/h · 15% saltStream 2350 kg/h · 35% saltStream 3x₃ = ? %

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

ṁ1 = 400 kg/hx1 = 15 %ṁ2 = 350 kg/hx2 = 35 %
x3 = %
2.Easy
MixerStream 1550 kg/h · 10% NaOHStream 2300 kg/h · 15% NaOHStream 3ṁ₃ = ? kg/h

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

ṁ1 = 550 kg/hx1 = 10 %ṁ2 = 300 kg/hx2 = 15 %
ṁ3 = kg/h
3.Medium
MixerStream 1900 kg/h · 45% 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 = 900 kg/hx1 = 45 %x2 = 5 %x3 = 25 %
ṁ2 = kg/h
4.Medium
MixerStream 1300 kg/h · 45% sugarStream 2ṁ₂ = ? · 5% 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 = 300 kg/hx1 = 45 %x2 = 5 %x3 = 20 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F3100 kg/h · 6% saltProduct P35% 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 = 3100 kg/hxF = 6 %xP = 35 %
W = kg/h
6.Hard
EvaporatorFeed F3900 kg/h · 10% saltProduct PP = ? · 50%Vapour W (pure water)0% salt

An evaporator concentrates a salt solution by boiling off pure water. Find the product flow P in kg/h.

F = 3900 kg/hxF = 10 %xP = 50 %
P = kg/h

Answer key

  1. 1. x3 = 24.33 %
  2. 2. ṁ3 = 850 kg/h
  3. 3. ṁ2 = 900 kg/h
  4. 4. ṁ2 = 500 kg/h
  5. 5. W = 2569 kg/h
  6. 6. P = 780 kg/h

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