2.3. Unsteady State and Mass Balances

Try these first

1. 1.

   Define unsteady state.

   Hint

   Think about how concentrations behave in dynamic systems.

2. 2.

   What is a mass balance?

   Hint

   Consider inputs, outputs, and changes in accumulation.

3. 3.

   What is the key difference between unsteady state and steady state?

   • Unsteady state has constant concentrations
   • Unsteady state has changing concentrations
   • Both states have the same concentration

   Hint

   Remember how systems vary over time.

4. 4.

   True or False: A mass balance looks at the rate of accumulation and the rate of loss.

   • True
   • False

   Hint

   Think about how inputs and outputs affect overall mass.

5. 5.

   If a river segment has an inflow of pollution at a concentration of 5 mg/L and outflow at 3 mg/L, calculate the net accumulation rate if the flow rate is 100 L/min.

   Hint

   Use the mass balance principles you learned.

6. 6.

   Model a scenario in which a lake's concentration of a pollutant increases due to a chemical reaction producing it at a rate of 50 mg/day while evaporation removes 20 mg/day. If the lake volume is constant, determine the new concentration after one day.

   Hint

   Consider using the mass balance formula for calculations.