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 1300 kg/h · 20% saltStream 2350 kg/h · 25% saltStream 3x₃ = ? %

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

ṁ1 = 300 kg/hx1 = 20 %ṁ2 = 350 kg/hx2 = 25 %
x3 = %
2.Easy
MixerStream 1300 kg/h · 40% NaOHStream 2450 kg/h · 5% NaOHStream 3x₃ = ? %

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

ṁ1 = 300 kg/hx1 = 40 %ṁ2 = 450 kg/hx2 = 5 %
x3 = %
3.Medium
MixerStream 1600 kg/h · 30% saltStream 2ṁ₂ = ? · 10% 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 = 600 kg/hx1 = 30 %x2 = 10 %x3 = 25 %
ṁ2 = kg/h
4.Medium
MixerStream 1900 kg/h · 5% saltStream 2ṁ₂ = ? · 45% saltProduct40% salt

How much of stream 2 must be added each hour to stream 1 so that the blended product contains 40% salt? Find ṁ2.

ṁ1 = 900 kg/hx1 = 5 %x2 = 45 %x3 = 40 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F3900 kg/h · 10% saltProduct P30% 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 = 3900 kg/hxF = 10 %xP = 30 %
W = kg/h
6.Hard
EvaporatorFeed F3200 kg/h · 20% sugarProduct PP = ? · 40%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 = 3200 kg/hxF = 20 %xP = 40 %
P = kg/h

Answer key

  1. 1. x3 = 22.69 %
  2. 2. x3 = 19 %
  3. 3. ṁ2 = 200 kg/h
  4. 4. ṁ2 = 6300 kg/h
  5. 5. W = 2600 kg/h
  6. 6. P = 1600 kg/h

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