Question

B. Calculation of Heat during phase change. A phase change is a physical process in which a substance goes from one phase to another. The temperature of a substance does not change as the substance goes from one phase to another. The heat of fusion (AHfus) is the amount of heat per gram (or per mole) required for a phase change that occurs at the melting point. The heat of vaporization, (Hvap) is the amount of heat per gram (or per mole) for a phase change that occurs at the boiling point. (Heats of Fusion and Vaporization for selected substances are given on p. 364-365 of your Textbook). The following expression applies. Q = mx AHfus where m = mass in g, Q = heat in calorie Q= m x ΔΗvap ΔΗfus; ΔΗ = cal/g 3. How much energy is needed to melt 43.8 g of Au at its melting point of 1,064°C?

Answer 1

cal (gram Solution How much energy is needed to melt 43.8 € of Au at its melting point of 1064°C We have the formula for Heat of fusion Q = mx AH fus) gram l tos We should have Attus for Au (Gold) So, we can tare p er tant In question, it is (referred to page 364-365 Alus value of Ay of textbook from google " (Affus gold = 12.5 kJ/mole Now, convert it in calorie / gram 12.5x1000 x 0.239 Calorie ir mole = 15017 Call ( 1 Joule = 0.239 cal] 197 le person = 15017 Now, Q = my(A Htus) Bal/gram Also, May = 197 gram UM = 43.8 x 15017 (0 = 665 Calorie. Auswer

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