The vapor pressure, P, of a certain liquid was measured at two temperatures If y

Question

The vapor pressure, P, of a certain liquid was measured at two temperatures If you were going to graphically determine the enthalpy of vaporizaton, dHvap, for this liquid, what points would you plot? The data is shown in this table. Number Number T(K) P (kPa) 325 3.91 875 9.00 To avoid rounding errors, use three significant figures in the x values and four significant figures in the y values. point 1 Number Number NOTE: Keep the pressure units in kPa oint 2: Determine the rise, run, and slope of the line formed by these points. rise run slope Number Number Number What is the enthalpy of vaporization of this liquid? Number vap J/mol no Previous R Give linViau, Cnl..

Explanation / Answer

we know that

the slope of the graph lnP vs 1/T can be used to obtain dHvap

so the x values will be 1/T and y values will be ln P

point 1 :

x = 1/325 = 0.00308

y = ln 3.91 = 1.364

point 2 :

x = 1/875 = 0.00114

y = ln 9 = 2.197

now

rise = y2 - y1 = 2.197 - 1.364 = 0.833

run = x2 - x1 = 0.00114 - 0.00308 = -0.00194

slope = rise / run = 0.833/ (-0.00194) = -429.3814433

now

we know that

slope = -dHvap / R = -429.3814433

dHvap = 429.3814433 x R = 429.3814433 x 8.314

dHvap = 3569.88 J /mol

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