Final answer:
Of the given gases, sulfur dioxide (option: D) has the greatest density at a temperature of 30°C and a pressure of 750 torr.
Step-by-step explanation:
The density of a gas depends on its molar mass and the temperature and pressure at which it is measured. To determine which gas has the greatest density at a temperature of 30°C and a pressure of 750 torr, we need to compare the molar masses of the gases. The gas with the greatest molar mass will have the greatest density.
Let's calculate the molar masses of the given gases:
A. Methane (CH4): 1 carbon atom (12.01 g/mol) + 4 hydrogen atoms (4.03 g/mol each) = 16.05 g/mol
B. Ammonia (NH3): 1 nitrogen atom (14.01 g/mol) + 3 hydrogen atoms (4.03 g/mol each) = 17.03 g/mol
C. Carbon dioxide (CO2): 1 carbon atom (12.01 g/mol) + 2 oxygen atoms (16.00 g/mol each) = 44.01 g/mol
D. Sulfur dioxide (SO2): 1 sulfur atom (32.07 g/mol) + 2 oxygen atoms (16.00 g/mol each) = 64.07 g/mol
From the calculations, we can see that sulfur dioxide (D) has the greatest molar mass and therefore the greatest density at the given temperature and pressure. So, the answer is D. sulfur dioxide.