At standard atmospheric pressure (1 atm), at what temperature does pure water boil?

• A. 100 °C
• B. 212 °C
• C. 0 °C
• D. 50 °C

Answer: (A)

Verified step by step guidance

1. Understand that the boiling point of a liquid is the temperature at which its vapor pressure equals the external pressure. At standard atmospheric pressure (1 atm), water boils when its vapor pressure reaches 1 atm.
2. Recall that the normal boiling point of water is defined as the temperature at which water's vapor pressure is exactly 1 atm under standard atmospheric pressure.
3. Recognize that for pure water at 1 atm pressure, this temperature is a well-known standard value, often used as a reference point in chemistry.
4. Identify that the standard boiling point of pure water at 1 atm is 100 °C, meaning water boils at 100 °C under these conditions.
5. Therefore, the temperature at which pure water boils at 1 atm pressure is 100 °C.