Question

Glycerin is being heated by flowing between two parallel 1-m-wide and 6-m-long plates with 12.5-mm spacing. The glycerin enters the parallel plates with a temperature of 25°C and a mass flow rate of 0.7 kg/s. The plates have a constant surface temperature of 40°C. Evaluate the properties for glycerin at 30°C. The properties of glycerin at 30°C are cp = 2447 J/kg∙K, k = 0.2860 W/m∙K, μ = 0.6582 kg/m∙s, and Pr = 5631. Is the temperature initially assumed for evaluating properties of glycerin approperiate?

Answer 1

To calculate the boiling point of a solution of glycerin in water, we can use the concept of boiling point elevation. The formula ΔTb = Kb × molality is used, where ΔTb is the boiling point elevation, Kb is the molal boiling point constant for the solvent, and molality is the molal concentration of the solute.

Step-by-step explanation:

In order to calculate the boiling point of a solution of glycerin in water, we need to use the concept of boiling point elevation. Boiling point elevation is a phenomenon where the boiling point of a solvent is raised when a solute is added to it.

The boiling point elevation can be calculated using the formula:

ΔTb = Kb × molality

Where:

• ΔTb is the boiling point elevation
• Kb is the molal boiling point constant for the solvent
• molality is the molal concentration of the solute

In this case, the solute is glycerin and the solvent is water. The mass of glycerin is given as 1.0 g and the mass of water is given as 47.8 g. To calculate the molality, we need to first convert the mass of glycerin to moles using its molar mass, and then divide it by the mass of water in kilograms.

Once we have the boiling point elevation, we can add it to the boiling point of pure water (which is 100°C at sea level) to find the boiling point of the solution.