CHM 2046C Module 7II Chapter 13 Sample Test Answers

Part U: Clausius-Clapeyron Equation Calculation 5 points

The Clausius-Clapeyron Equation (13.2-page 612) is:

Ln P₂/P₁ = ΔH^o_vap/R [(T₂ - T₁)/T₁T₂]

Calculate the enthalpy of vaporization of diethyl ether, (C₂H₅)₂O. From Figure 13.18 on page 610 Diethyl ether has vapor pressures of 57.0 torre and 534 torre at -22.8^oC and 25.2^oC respectively.

R from the ideal gas constant is 8.3145 J/K∙mol

Ln(534 torre/57.0 torre) = ΔH^o_vap /8.3145 J/K∙mol [(298.2K - 250.2K)/250.2K∙ 298.2K ]

(2.237)(8.3145 J/K∙mol) = ΔH^o_vap [47.8/250.2K∙ 298.2K]/K

(2.237)(8.3145 J/K∙mol) = ΔH^o_vap [xxx]/K

(18.60 J/mol) / xxxx = ΔH^o_vap

29,100 J/mol = 29.1 kJ/mol = ΔH^o_vap

For additional Homework, work problems #21 & #22 on pages 635-636.