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 1350 kg/h · 15% NaOHStream 2400 kg/h · 20% NaOHStream 3x₃ = ? %

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

ṁ1 = 350 kg/hx1 = 15 %ṁ2 = 400 kg/hx2 = 20 %
x3 = %
2.Easy
MixerStream 1200 kg/h · 40% saltStream 2700 kg/h · 35% saltStream 3x₃ = ? %

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

ṁ1 = 200 kg/hx1 = 40 %ṁ2 = 700 kg/hx2 = 35 %
x3 = %
3.Medium
MixerStream 1300 kg/h · 20% saltStream 2ṁ₂ = ? · 40% saltProduct30% salt

How much of stream 2 must be added each hour to stream 1 so that the blended product contains 30% salt? Find ṁ2.

ṁ1 = 300 kg/hx1 = 20 %x2 = 40 %x3 = 30 %
ṁ2 = kg/h
4.Medium
MixerStream 1250 kg/h · 50% saltStream 2ṁ₂ = ? · 5% saltProduct45% salt

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

ṁ1 = 250 kg/hx1 = 50 %x2 = 5 %x3 = 45 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F1600 kg/h · 13% sugarProduct P40% 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 = 1600 kg/hxF = 13 %xP = 40 %
W = kg/h
6.Hard
EvaporatorFeed F3700 kg/h · 7% saltProduct PP = ? · 30%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 = 3700 kg/hxF = 7 %xP = 30 %
P = kg/h

Answer key

  1. 1. x3 = 17.67 %
  2. 2. x3 = 36.11 %
  3. 3. ṁ2 = 300 kg/h
  4. 4. ṁ2 = 31.25 kg/h
  5. 5. W = 1080 kg/h
  6. 6. P = 863.3 kg/h

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