A certain liquid has a vapor pressure of 92.0 Torr at 23.0 °C and 351.0 Torr at 45.0 °C. Calculate the value of ΔH°vap for this liquid.

Respuesta :

there is a specific formula to use for these type of problems. 

ln (P2/ P1)= Δvap/ R x (1/T1 - 1/T2)

R= 8.314
P1= 92.0 torr
T1= 23 C + 273= 296 K
P2= 351.0 torr
T2= 45.0 C + 273= 318 K

plug the values and solve for the unknown

ln( 351.0/ 92.0)= Δvap/ 8.314 x (1/296 - 1/318)

Δvap= 47630.6 joules

Ver imagen JavierCollante

Answer : The value of [tex]\Delta H_{vap}[/tex] is 47.627 kJ/mol

Explanation :

To calculate [tex]\Delta H_{vap}[/tex] of the reaction, we use clausius claypron equation, which is:

[tex]\ln(\frac{P_2}{P_1})=\frac{\Delta H_{vap}}{R}[\frac{1}{T_1}-\frac{1}{T_2}][/tex]

where,

[tex]P_1[/tex] = vapor pressure at temperature [tex]23^oC[/tex] = 92 torr

[tex]P_2[/tex] = vapor pressure at temperature [tex]45^oC[/tex] = 351 torr

[tex]\Delta H_{vap}[/tex] = Enthalpy of vaporization = ?

R = Gas constant = 8.314 J/mol K

[tex]T_1[/tex] = initial temperature = [tex]23^oC=[23+2730]K=296K[/tex]

[tex]T_2[/tex] = final temperature = [tex]45^oC=[45+2730]K=318K[/tex]

Putting values in above equation, we get:

[tex]\ln(\frac{351torr}{92torr})=\frac{\Delta H_{vap}}{8.314J/mol.K}[\frac{1}{296}-\frac{1}{318}]\\\\\Delta H_{vap}=47627.347J/mol=47.627kJ/mol[/tex]

Therefore, the value of [tex]\Delta H_{vap}[/tex] is 47.627 kJ/mol