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 1800 kg/h · 15% NaOHStream 2350 kg/h · 20% NaOHStream 3x₃ = ? %

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

ṁ1 = 800 kg/hx1 = 15 %ṁ2 = 350 kg/hx2 = 20 %
x3 = %
2.Easy
MixerStream 11000 kg/h · 20% saltStream 21000 kg/h · 25% saltStream 3x₃ = ? %

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

ṁ1 = 1000 kg/hx1 = 20 %ṁ2 = 1000 kg/hx2 = 25 %
x3 = %
3.Medium
MixerStream 1300 kg/h · 10% sugarStream 2ṁ₂ = ? · 50% 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 = 300 kg/hx1 = 10 %x2 = 50 %x3 = 45 %
ṁ2 = kg/h
4.Medium
MixerStream 1450 kg/h · 50% NaOHStream 2ṁ₂ = ? · 20% NaOHProduct40% NaOH

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

ṁ1 = 450 kg/hx1 = 50 %x2 = 20 %x3 = 40 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F1000 kg/h · 16% NaOHProduct PP = ? · 30%Vapour W (pure water)0% NaOH

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

F = 1000 kg/hxF = 16 %xP = 30 %
P = kg/h
6.Hard
EvaporatorFeed F4600 kg/h · 16% NaOHProduct P50% 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 = 4600 kg/hxF = 16 %xP = 50 %
W = kg/h

Answer key

  1. 1. x3 = 16.52 %
  2. 2. x3 = 22.5 %
  3. 3. ṁ2 = 2100 kg/h
  4. 4. ṁ2 = 225 kg/h
  5. 5. P = 533.3 kg/h
  6. 6. W = 3128 kg/h

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