Question

The following temperature and pressure data were collected for an unknown liquid.

Table: Temperature and Pressure of an Unknown Liquid

Temperature (°C)	Pressure (mmHg)
5	50.757
10	67.952
15	90.497
20	119.24
25	155.04
30	200.44
35	256.98
40	326.87
45	412.21
50	518.69
55	645.60
60	798.31
65	977.03
70	1197.0

Using the relationship

ln P = −ΔH_{vap /R (1/T) + C}

graph the data and determine the ΔH_vap for the liquid. (Enter your answer to three significant figures.)
kJ/mol

Answer 1

Ans.

1.000 Temp 0.500 0.000 0.00000 0.00050 0.00100 0.00150 0.00200 0.00250 0.0000 0.00350 0.00400 -0.500 Vap 2-1.000 P mmHg 50.757 67.952 90.497 119.24 155.04 200.44 256.98 326.87 412.21 518.69 645.6 798.32 977.03 1197 Temp K 278.15 283.15 288.15 293.15 298.15 303.15 308.15 313.15 318.15 323.15 328.15 333.15 338.15 343.15 atm 0.06679 0.08941 0.11908 0.15689 0.20400 0.26374 0.33813 0.43009 0.54238 0.68249 0.84947 1.05042 1.28557 1.57500 1/K In Pvap 0.00360 -2.706 0.00353 -2.415 0.00347 -2.128 0.00341 -1.852 0.00335 -1.590 0.00330 -1.333 0.00325 -1.084 0.00319 -0.844 0.00314 -0.612 0.00309 -0.382 0.00305 -0.163 0.00300 0.049 0.00296 0.251 0.00291 0.454 -1.500 y = -4642.1x + 13.981 R2 = 1 -2.000 -2.500 -3.000 1/T Slope, m= -AH Vap So, AHMap = -(m x R) = 4642.1 K x 0.008314 k] mol-1 K1 = 38.6 kJ mol-1