How much heat is required to vaporize 64 g of methanol? 19 kJ 38 kJ 57 kJ 76 kJ?

Question

How much heat is required to vaporize 64 g of methanol? 19 kJ 38 kJ 57 kJ 76 kJ? The normal boiling point of a substance is defined to be the temperature at which the liquid phase of the substance is in equilibrium with the gas phase at 1 atm pressure. If the normal boiling point of methanol is 80 degree C and the Delta H degree _vap is 38 kJ/mol, what is Delta S degree _vap at 80 degree C? + 108 J/mol-K - 108 J/mol-K + 475 J/mol-K - 475 J/mol-K + 3040 J/mol-K Which of the following correctly expresses the relationship between the enthalpy of a system and the entropy of the surroundings? At 25 degree C dry ice (solid carbon dioxide) spontaneously sublimes: CO_2(s) rightarrow CO_2 (g) Given than Delta H_SUB degree = 15 J/mol and Delta S_SUB degree = 140 J/mol-K, what is Delta S_UNIV for this process? Delta S_UNIV = 0 J/mol-K Delta S_UNIV = + 90 J/mol-K Delta S_UNIV = + 140 J/mol-K Delta S_UNIV = + 190 J/mol-K Delta S_UNIV = - 460 J/mol-K

Explanation / Answer

Ssurroundings = -H/T = -15 x 103/(273+25) = -50 J/mol-K

Ssystem = 140 J/mol-K

Suniverse = Ssurroundings + Ssystem = (-50+140) J/mol-K = 90 J/mol-K

Answer is option (B) 90 J/mol-K.

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