Final answer:
The vapor pressure of water at 20°C is not specified among the given options since it is significantly lower than 1 atm, which is the atmospheric pressure at the boiling point of water (100°C at sea level).
Step-by-step explanation:
The question regarding the vapor pressure of water at a specific temperature falls under the category of Chemistry. Vapor pressure is the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases (solid or liquid) at a given temperature in a closed system.
The vapor pressure of water increases with temperature until it reaches atmospheric pressure (1 atm) at its boiling point, which is 100°C at sea level.
Since the question asks for the vapor pressure of water at 100/5°C, which is 20°C, we need to refer to a vapor pressure table or use Antoine's equation to find the exact value. However, without such data or the ability to calculate it, we cannot specify the precise vapor pressure.
None of the given options (1 atm, 0.760 atm, 0.995 atm, 0.789 atm) correspond to the vapor pressure of water at 20°C, since water's vapor pressure at this temperature is significantly lower than 1 atm. Therefore, the correct answer is not listed among the given options.