The binary diffusivity of a particular salt in water at room temperature is 3.2 × 10⁻⁴ cm²/s. That salt in solid form dissolves at the bottom of a beaker of water (8 cm high), while water flows across the top of the beaker at a high velocity, as shown.

The concentration of the dissolved salt equals its saturation value (csat) at the top surface of the solid, and it equals 0 at the top of the beaker (because of the high flow rate of the water flowing across). When the water inside the beaker is stirred at a particular rate, the solid dissolves at a rate 4 times greater than when the water in the beaker is not stirred (sits stationary). What is the value of the mass-transfer coefficient in the stirred condition (numerical value and units)?

Transcribed Image Text:

8 cm Fast-moving Water Water c=0 c=csat Dissolving Solid