Explain what the Clapeyron equation describes. b. Explain what the Clausius-Clap

Question

Explain what the Clapeyron equation describes. b. Explain what the Clausius-Clapeyron equation describes. c. Calculate the boiling temperature of water at an elevation of 1700 m (approximately the height of Boulder, CO) given that atmospheric pressure there is about 0.83 atm. You may refer to the CHEM 452 units table (on Canvas under 'Files', 'miscellaneous', for information on water properties. d. Calculate the (equilibrium) sublimation temperature of CO_2 at a pressure of 2 atm assuming a constant enthalpy of sublimation of Delta H=26 kJ/mol. The sublimation temperature of C02 at 1 atm is -78.5 degree C. e. Gold has an equilibrium melting temperature of 1337 K at 1 atm and an enthalpy of fusion of 12, 550 J/mol. Find the pressure at which the equilibrium melting temperature is 1400 K. The densities of solid gold and liquid gold are 19.3 g/mL and 17.3 g/mL and are assumed to be approximately constant under all conditions. f. (Gold, continued.) Using your answer from part e), calculate the entropy change for melting 1 mol of gold.

Explanation / Answer

a.

This equation relates

The slopes of the lines on a one component pressure vs. temperature phase diagram may be derived from the Clapeyron equation.

it mainly relates :

dp = dH/dV * dT/T

b.

The equation:

ln(P2/P1) = H/R*(1/T1-1/T2)

it describes:

- Relation between at leas two points

- Assumes equilibrium phases are striaght lines!

- Slope is -H/R or entahlpy of phase change dvided by ideal gas constant

- Relates Psat with Tsat

c.

find

ln(P2/P1) = H/R*(1/T1-1/T2)

ln(0.83/1) = 40700/8.3614*(1/393-1/T2)

Solve for T2

T2 = -(-0.1863*8.3614/40700 - 1/393)^-1

T2 = 387 K = 114 °C

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