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 1650 kg/h · 40% NaOHStream 2900 kg/h · 30% NaOHStream 3x₃ = ? %

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

ṁ1 = 650 kg/hx1 = 40 %ṁ2 = 900 kg/hx2 = 30 %
x3 = %
2.Easy
MixerStream 1700 kg/h · 15% sugarStream 2350 kg/h · 35% sugarStream 3x₃ = ? %

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

ṁ1 = 700 kg/hx1 = 15 %ṁ2 = 350 kg/hx2 = 35 %
x3 = %
3.Medium
MixerStream 1900 kg/h · 50% sugarStream 2ṁ₂ = ? · 20% sugarProduct45% sugar

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

ṁ1 = 900 kg/hx1 = 50 %x2 = 20 %x3 = 45 %
ṁ2 = kg/h
4.Medium
MixerStream 1350 kg/h · 35% saltStream 2ṁ₂ = ? · 15% 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 = 350 kg/hx1 = 35 %x2 = 15 %x3 = 30 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F1800 kg/h · 15% NaOHProduct P55% 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 = 1800 kg/hxF = 15 %xP = 55 %
W = kg/h
6.Hard
EvaporatorFeed F3900 kg/h · 15% saltProduct P45% 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 = 15 %xP = 45 %
W = kg/h

Answer key

  1. 1. x3 = 34.19 %
  2. 2. x3 = 21.67 %
  3. 3. ṁ2 = 180 kg/h
  4. 4. ṁ2 = 116.7 kg/h
  5. 5. W = 1309 kg/h
  6. 6. W = 2600 kg/h

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