A steady mixer combines 100 kg/h solution containing 10 wt% solute with 50 kg/h solution containing 30 wt% solute. Product solute mass fraction is most nearly:
- (A)0.1
- (B)0.167
- (C)0.2
- (D)0.3
Show worked solution
Answer: (B)
Solute flow is 10+15=25 kg/h in 150 kg/h product, so mass fraction is 0.1667.
Total and solute balances both apply to the nonreactive mixer.
Product composition is component flow divided by total flow.
FE Reference Handbook — Material Balances: Steady Mixing
Why the other choices appear
- (A)Using only the dilute feed composition ignores the concentrated stream.
- (C)Taking an unweighted average ignores unequal feed flow rates.
- (D)Using only the concentrated feed composition ignores dilution.