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 1900 kg/h · 40% sugarStream 21000 kg/h · 15% sugarStream 3x₃ = ? %

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

ṁ1 = 900 kg/hx1 = 40 %ṁ2 = 1000 kg/hx2 = 15 %
x3 = %
2.Easy
MixerStream 1100 kg/h · 35% sugarStream 2850 kg/h · 15% sugarStream 3ṁ₃ = ? kg/h

Two sugar solutions are mixed at steady state. Find the outlet flow rate ṁ3.

ṁ1 = 100 kg/hx1 = 35 %ṁ2 = 850 kg/hx2 = 15 %
ṁ3 = kg/h
3.Medium
MixerStream 1250 kg/h · 15% 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 = 250 kg/hx1 = 15 %x2 = 45 %x3 = 40 %
ṁ2 = kg/h
4.Medium
MixerStream 1400 kg/h · 35% sugarStream 2ṁ₂ = ? · 5% sugarProduct10% sugar

How much of stream 2 must be added each hour to stream 1 so that the blended product contains 10% sugar? Find ṁ2.

ṁ1 = 400 kg/hx1 = 35 %x2 = 5 %x3 = 10 %
ṁ2 = kg/h
5.Hard
EvaporatorFeed F3400 kg/h · 8% saltProduct PP = ? · 35%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 = 3400 kg/hxF = 8 %xP = 35 %
P = kg/h
6.Hard
EvaporatorFeed F900 kg/h · 17% sugarProduct P45% 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 = 900 kg/hxF = 17 %xP = 45 %
W = kg/h

Answer key

  1. 1. x3 = 26.84 %
  2. 2. ṁ3 = 950 kg/h
  3. 3. ṁ2 = 1250 kg/h
  4. 4. ṁ2 = 2000 kg/h
  5. 5. P = 777.1 kg/h
  6. 6. W = 560 kg/h

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