Question

2. In the ice cream making process, after the pasteurization of the base mixture, the syrup should be cooled to 4 °C to avoid the proliferation of pathogenic microorganisms. A new thermometer was attached to the tank; however, it marked a temperature in another unit: Rankine. What should be the value indicated on the thermometer for the process to be carried out under the same conditions?

3. During the class in the laboratory, the manometer coupled to the analysis equipment indicates a vacuum of 638 mmHg. What should be the absolute pressure in kPa and psi, knowing that the local barometric pressure is 101.3 kPa?

Answer 1

2. 500 R

3. 16.3 kPa, 2.36 psi

Step-by-step explanation:

2. Convert Celsius to Fahrenheit.

1.8 (4°C) + 32 = 39.2°F

Convert Fahrenheit to Rankine

39.2°F + 459.67 = 498.87 R

Rounding to one significant figure, the temperature is 500 R.

3. Absolute pressure = gauge pressure + atmospheric pressure

P = Pg + Pa

First, convert mmHg to kPa (remember that a vacuum is negative gauge pressure).

-638 mmHg × (101.3 kPa / 760 mmHg) = -85.0 kPa

So the absolute pressure is:

P = -85.0 kPa + 101.3 kPa

P = 16.3 kPa

Converting to psi:

P = 16.3 kPa × (14.7 psi / 101.3 kPa)

P = 2.36 psi