Question

Before the introduction of chlorofluorocarbons, sulfur dioxide (enthalpy of vaporization, 6.00 kcal/mol) was used in household refrigerators. What mass of SO2 must be evaporated to remove as much heat as evaporation of 1.00 kg of CCl2F2 (enthalpy of vaporization is 17.4 kJ/mol)?

a) 10.5 g
b) 21.0 g
c) 35.7 g
d) 40.0 g

Answer 1

To remove the same amount of heat as 1.00 kg of CCl2F2, a mass of 367.2 g of SO2 must be evaporated. This value is calculated using the enthalpy of vaporization for both substances and their respective molar masses.

Step-by-step explanation:

To find out what mass of sulfur dioxide (SO2) is required to remove the same amount of heat as 1.00 kg of dichlorodifluoromethane (CCl2F2), we first need to calculate the total heat removed by the evaporation of CCl2F2. The molar mass of CCl2F2 is approximately 120.91 g/mol. So, 1.00 kg of CCl2F2 is approximately 8.27 mol (1000 g / 120.91 g/mol).

Using the enthalpy of vaporization for CCl2F2 which is 17.4 kJ/mol, the total heat removed by its evaporation is 143.9 kJ (8.27 mol × 17.4 kJ/mol). Now, convert the enthalpy of vaporization of SO2 from kcal/mol to kJ/mol, which is 25.1 kJ/mol (6.00 kcal/mol × 4.184 kJ/kcal).

To remove 143.9 kJ using SO2, we divide the heat by the enthalpy of vaporization of SO2 to find moles needed. 143.9 kJ / 25.1 kJ/mol gives us approximately 5.73 mol of SO2. The molar mass of SO2 is 64.07 g/mol, giving a mass of 367.2 g (5.73 mol x 64.07 g/mol). Therefore, to remove as much heat as the evaporation of 1.00 kg of CCl2F2, a mass of 367.2 g of SO2 must be evaporated, which is not one of the options provided in the question, indicating a possible error in the question data.