HEAT IN CHANGES OFSTATE. Terminologies . MOLAR HEAT: it is the enthalpy changes( Δ H) for 1 mole of substance to change a state. Molar Heat of Fusion ( Δ H fus ): the amount of heat absorbed by 1 mole of a substance in melting from solid to a liquid. Exothermic or Endothermic?
the heat change caused by dissolution of 1 mole of substance. Exothermic or Endothermic?
Q or ΔH (kJ)= number of moles of a substance (mol) x Molar heat of substance (kJ/mol) OR
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. 3240 joules c. 0.0111 joules
b. –2004 joules d. 0.018 joules
a. 48,600 joules c. 0.0398 joules
b. 0.1667 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. –0.3982 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. 2.7778 g c. 0.02 g
b. 0.36 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 oCliquid iron can be turned into 2750 oCiron vapor if 70,000 kJ of energy are given to the molten iron?
a. 3.5812 g c. 11,169 g
b. 0.005 g d. 0.27924 g