ANS:B - 1.013

The vapor pressure of water at a specific temperature is the pressure exerted by water vapor when it is in equilibrium with liquid water at that temperature. At 100°C, which is the boiling point of water at standard atmospheric pressure (1 atm), the vapor pressure of water is approximately 1.013 bar. This value of 1.013 bar is significant because it corresponds to the standard atmospheric pressure at sea level. At this pressure, water boils at 100°C. When water reaches its boiling point, its vapor pressure equals the atmospheric pressure, causing bubbles of vapor to form within the liquid and escape into the air. As a result, the vapor pressure of water at this temperature is 1.013 bar, which is equivalent to the standard atmospheric pressure at sea level. This value is a key reference point in many applications, including cooking, thermodynamics, and meteorology. It helps in understanding the behavior of water and other substances at different temperatures and pressures.