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[forum12345]

A solution composed of 50% ethanol (EtOH), 10% methanol (MeOH), and 40% water (H2O) is fed at the rate of 100 kg/hr into a separator that produces one stream at the rate of 60 kg/hr with the composition of 80% EtOH, 15% MeOH, and 5% H2O, and a second stream of unknown composition. Calculate the composition (in %) of the three compounds in the unknown stream and its flowrate in kg/hr.


MASS BALANCE!!! assuming no reaction in=out
so starting with the flowrate

100 kg/hr IN = 60 kg/hr + x kg/hr OUT
the unknown stream is 40 kg/hr

now we do this individually for each component
for ethanol
we have (50%)(100 kg/ hr)= 50 kg/hr IN
therefore we must have 50 kg/hr coming OUT
so we sum the ethanol coming out (i.e. we add up the amount of ethanol in stream 1 coming up and the amount of ethanol in stream 2 coming out)
(80%)(60 kg/hr) + a(40 kg/hr) = 48 + 40a = 50
from that we can figure out a=(50-48)/40=2/40=5%

repeat for the other components!
Is this correct

[demank]

Yes, correct.., the answer is:
EtOH 5% (2 kg/hr)
MeOH 2.5% (1 kg/hr)
H2O 92.5% (37 kg/hr)