Which of the following is closest to the vapor pressure of propanone (acetone) at 45 °C?

• A. 80 kPa
• B. 56 kPa
• C. 101 kPa
• D. 40 kPa

Answer: (B)

Verified step by step guidance

1. Identify the key concept: vapor pressure is the pressure exerted by a vapor in equilibrium with its liquid at a given temperature. It depends strongly on temperature and the nature of the liquid.
2. Recall or find the vapor pressure data for propanone (acetone) at 45 °C from a reliable source such as a vapor pressure table or graph. Vapor pressure values are often tabulated or can be estimated using the Antoine equation.
3. If using the Antoine equation, the formula is: \(\log_{10} P = A - \frac{B}{C + T}\), where \(P\) is the vapor pressure, \(T\) is the temperature in °C, and \(A\), \(B\), and \(C\) are substance-specific constants. Plug in the constants for acetone and the temperature 45 °C to calculate \(P\).
4. Convert the vapor pressure to the desired units if necessary (e.g., from mmHg to kPa) using the conversion factor: \$1\ \text{atm} = 101.3\ \text{kPa} = 760\ \text{mmHg}$.
5. Compare the calculated or looked-up vapor pressure value to the given options (80 kPa, 56 kPa, 101 kPa, 40 kPa) and select the closest one.