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 1550 kg/h · 30% NaOHStream 2800 kg/h · 40% NaOHStream 3x₃ = ? %

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

ṁ1 = 550 kg/hx1 = 30 %ṁ2 = 800 kg/hx2 = 40 %
x3 = %
2.Easy
MixerStream 1450 kg/h · 40% saltStream 2600 kg/h · 35% saltStream 3x₃ = ? %

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

ṁ1 = 450 kg/hx1 = 40 %ṁ2 = 600 kg/hx2 = 35 %
x3 = %
3.Medium
MixerStream 1450 kg/h · 20% sugarStream 2ṁ₂ = ? · 50% sugarProduct25% sugar

How much of stream 2 must be added each hour to stream 1 so that the blended product contains 25% sugar? Find ṁ2.

ṁ1 = 450 kg/hx1 = 20 %x2 = 50 %x3 = 25 %
ṁ2 = kg/h
4.Medium
MixerStream 1700 kg/h · 50% sugarStream 2ṁ₂ = ? · 10% sugarProduct30% sugar

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

ṁ1 = 700 kg/hx1 = 50 %x2 = 10 %x3 = 30 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F4000 kg/h · 6% 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 = 4000 kg/hxF = 6 %xP = 40 %
W = kg/h
6.Hard
EvaporatorFeed F3000 kg/h · 8% NaOHProduct P60% NaOHVapour W (pure water)W = ? kg/h

An evaporator concentrates a NaOH solution by boiling off pure water. Find the water evaporated W in kg/h.

F = 3000 kg/hxF = 8 %xP = 60 %
W = kg/h

Answer key

  1. 1. x3 = 35.93 %
  2. 2. x3 = 37.14 %
  3. 3. ṁ2 = 90 kg/h
  4. 4. ṁ2 = 700 kg/h
  5. 5. W = 3400 kg/h
  6. 6. W = 2600 kg/h

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