Cobalt chloride hexahydrate, CoCl2 6H2O, is a bright pink compound, but in the presence of very dry air it loses water vapor to the air to produce the light blue anhydrous salt CoCl2. Calculate the standard free-energy change for the reaction at 25oC:

Here are some thermodynamic data at 25oC:

What is the partial pressure of water vapor in equilibrium with the anhydrous salt and the hexahydrate at 25oC? (Give the value in mmHg.) What is the relative humidity of air that has this partial pressure of water? The relative humidity of a sample of air is
Relative humidity = partial pressure of H2O (g) in air/vapor pressure of water ×100%
What do you expect to happen to the equilibrium partial pressure over the hexahydrate as the temperature is raised? Explain

Transcribed Image Text:

CoC12-6H20(s)--CoCl2(s) + 6H20(g) AHo (kJ/mol) AG (kJlmol) So (Jlmol K) -313 CoCI2(s) CoC2 6H202115 -270 1725. 109. 343