U\'se the References to access Importast values if needed for this at its normal

Question

U'se the References to access Importast values if needed for this at its normal melting point of-112C is 4.4 k/mol, while its heat of vaporization at its normal boiling point of 46 'C is 26.7 kJmol. (a) Use these data to calculate the heat of sublimation for CS2 is your answer precise or is it approximate? (b) At 298 k, the standard heat of formation of CS,(0) is 89.0 kJ/mol while the standard beat of formation of CS,(g) is 116.7 kJ/mol. Use this to calculate the heat of vaporization of kJ/mol carbon disulfide. k/mol Is your result for part (b) larger or smaller than the value given in the statement of the problem? Submit Answer

Explanation / Answer

Sublimation is the process of conversion of solid directly to liquid. Thus, Heat of sublimation = Heat of fusion + Heat of vaporization = (4.4+26.7)KJ/mol = 31.1 KJ/mol. It is approximate because the heats of fusion and vaporization are measured at different temperatures. At 298K, CS2 (l) forms from its constituent elements, the energy required to do so is given as 89.0KJ/mol. Then, it takes in energy equal to the heat of vaporisation and converts to CS2(g). Thus, heat of vaporisation = (116.7-89.0)KJ/mol = 27.7KJ/mol. It is larger than given value because we haven't considered the heat energy required to take CS2 from 298K to its boiling point, i.e, 319K.

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