 MOLAR HEAT: it is the enthalpy changes(ΔH) for 1 mole of substance to change a state.  Molar Heat of Fusion (ΔH fus ): the amount of heat absorbed by 1 mole of a substance in melting from solid to a liquid. Exothermic or Endothermic?  Molar Heat of Solidification (ΔH solid ): the amount heat lost when 1 mole of a liquid solidifies or freezes at a constant temperature. Exothermic or Endothermic?

 Molar Heat of Vaporization (ΔHvap): the amount of heat needed to vaporize 1 mole of a liquid. Exothermic or Endothermic?  Molar heat of Condensation (ΔHcond): the amount of heat released or lost when 1 mole of vapor condenses or cools down to form liquid. Exothermic or Endothermic?

the heat change caused by dissolution of 1 mole of substance. Exothermic or Endothermic?

 ΔH fus = - ΔH solid  ΔH vap = -ΔH cond 

 Q or q: stands for the amount of heat absorbed or released for any given number of moles of substance.  S.I. unit for Q or ΔH (amount of heat) is in Joules (J)  The unit for molar heat: ΔH fus, or ΔH vap or ΔH soln is in kJ/mol. Also in cal/g or J/g  Remember: 1000J = 1kJ and 1J= cal

 Q or ΔH (kJ)= number of moles of a substance (mol) x Molar heat of substance (kJ/mol) OR  Q or ΔH (kJ)= mass (g) x inverted molar mass (mol/g) x Molar heat of substance (kJ/mol)  OR  Q or ΔH (cal)= mass (g) x Molar heat of substance (cal/g)

 According to law of conservation of energy:  If Molar heat of fusion (ΔH fus ) for water is 6.01kJ/mol therefore, the Molar heat of Solidification (ΔH solid ) for water would be -6.01kJ

1. assuming no temperature change? The heat of fusion of copper is about 0.2 kJ/g. a. 80 kJ c. 88,000 kJ b. 40 kJ d. 1,000 kJ 2. What is Q when 6 grams of water freezes at the freezing point, with no temperature change? a joules c joules b. –2004 joules d joules

3. What is the latent heat (Q) when 90 grams of water vapor condenses? a. 48,600 joules c joules b joules d. –203,400 joules 4. What is the change in thermal energy content of 900 grams of water when it vaporizes? a. –0.6 calories c. –2,034,000 calories b. – calories d. 486,000 calories

5. An ice cube in a well-mixed glass of ice water is melting at the melting point. How much of the ice will melt if the ice cube gains 4,000 calories of energy? a g c g b g d. 50 g 6. A vat of liquid iron is at its boiling point, 2750 oC. The latent heat of vaporization of iron is 350 kJ/mol. How much of the 2750 oC liquid iron can be turned into 2750 oC iron vapor if 70,000 kJ of energy are given to the molten iron? a g c. 11,169 g b g d g