Mass Transfer

Step 1: Understanding the dissolution process.
The dissolution rate is governed by the surface area of the tablet. For a sphere, the surface area is proportional to (where is the radius of the sphere), and for a cube, the surface area is proportional to (where is the side length of the cube). Since the amount of drug in both tablets is the same, we use the surface area to determine the dissolution rate. The surface area to volume ratio for a sphere and a cube differs. For a sphere, the surface area to volume ratio is higher than that for a cube.
Step 2: Surface area and volume ratios.
For the sphere, surface area to volume ratio is: For the cube, surface area to volume ratio is: Given that the total mass of the drug is the same, the dissolution rate is inversely proportional to the surface area to volume ratio. The ratio of the dissolution rates of a cube to a sphere is 0.54.
Step 3: Conclusion.
The correct answer is (1), 0.54.

Step 1: Understanding the drying rate.
The drying rate during the constant rate period can be calculated using the formula for convective drying, where the drying rate is determined by the heat transfer and latent heat of vaporization. The formula for the drying rate is: Where: - is the heat transfer coefficient (11 W/m K) - is the surface area (not given, but assumed to be 1 for simplicity) - is the temperature difference between the air and the surface ( ) - is the latent heat of vaporization of water (2500 kJ/kg) Step 2: Calculating the drying rate.
Using the given values and converting the latent heat to J/kg (2500 kJ/kg = 2.5 × 10 J/kg), we find the drying rate: Step 3: Conclusion.
The drying rate is 0.00453 kg/s. The correct answer is .