The Clausius-Clapeyron equation allows calculation of the vapor pressure of a li
ID: 978204 • Letter: T
Question
The Clausius-Clapeyron equation allows calculation of the vapor pressure of a liquid at different temperatures. The equation follows: ln (P_1/P_2) = delta H_vap/R (1/T_2 - 1/T_1) R = 8.314 J/mol-K Diethyl ether is a volatile, highly flammable organic liquid that is used mainly as a solvent. The vapor pressure of diethyl ether is 401 mmHg at 18 degree C. Calculate its vapor pressure at 32 degree C. Use 26.0 kJ/mol for delta H_vap. The boiling point and freezing point of a compound are -205 degreeC and -160 degree C (at one atmosphere), respectively. The triple point is at -200 degree C and 1.01 * 10^-2 atm, and its critical point is at -90 degree C and 78 atm. On the basis of this information, draw a rough sketch of the phase diagram of the compound. On the phase diagram label the regions, the triple point, the critical point, and the supercritical fluid region. What are the boiling point and freezing point of a 2.47 m solution of naphthalene in benzene The boiling point and freezing point of benzene are 80.1 degree C and 5.5 degree C, respectively. For benzene, the K_b = 2.53 degree C/m, and the K_1 = 5.12 degree C/m. A solution of 2.50 g of a compound having the empirical formula C_6H_5P in 25.0 g benzene is observed to freeze at 4.3 degree C. Calculate the molar mass of the solute and its molecular formula. See problem 3 for the constants needed.Explanation / Answer
1) Substituting the given data in the Clausius-Clapeyron eqn
2.303 log (P2/401mm) = 26000 Jmol-1/8.314 JK-1mol-1 [ (305 K- 291K)/ (305K)(291K)]
log P2 = 3.73
P2= 5370.3 mm.