Final answer:
The partial pressure of neon in a mixture of helium and neon gases collected over water at 28.0°C and a total pressure of 745 mmHg, with helium having a partial pressure of 368 mmHg, is 348.7 mmHg.
Step-by-step explanation:
The calculation of the partial pressure of neon when a mixture of helium and neon gases is collected over water requires us to apply Dalton's Law of partial pressures. According to this law, the total pressure of a mixture of gases is equal to the sum of the partial pressures of the individual gases. In the scenario described, the total pressure of the mixture (745 mmHg) is the sum of the partial pressure of helium, the partial pressure of neon, and the vapor pressure of water at the given temperature.
The partial pressure of helium is given as 368 mmHg, and the vapor pressure of water at 28.0°C is 28.3 mmHg. Therefore, to find the partial pressure of neon, we subtract the partial pressure of helium and the vapor pressure of water from the total pressure:
Partial pressure of neon = Total pressure - (Partial pressure of helium + Vapor pressure of water)
Partial pressure of neon = 745 mmHg - (368 mmHg + 28.3 mmHg)
Partial pressure of neon = 745 mmHg - 396.3 mmHg
Partial pressure of neon = 348.7 mmHg