Mastering Chemistry—Chapter 12 Questions (Part 2) #8 $9 #14 Part A: A 50.0 mL sa

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Mastering Chemistry—Chapter 12 Questions (Part 2)

#8

$9

#14

Part A: A 50.0 mL sample of water is heated to its boiling point. How much heat is required to vaporize it? (Assume a density of 1.00 g/mL.) Express the heat in kilojoules to three significant figures.

#15

Part A Calculate the amount of heat (in kilojoules) required to vaporize 2.58 kg of water at its boiling point. Express the heat in kilojoules to three significant figures q= 5830 kJ Submit My Answers Give Up Correct At its boiling point, the enthalpy of vaporization (AHvap) of water is 40.7 kJ/mol. Once the given mass, 2.58 × 103 g, is converted to the number of moles using the molar mass of water (18.02 g/mol), multiplying the number of moles by ap yields the amount of heat required to evaporate that amount of water Part B Suppose that 0.48 g of water at 25° C condenses on the surface of a 55-g block of aluminum that is initially at 25 C. If the heat released during condensation goes only toward heating the metal, what is the final temperature (in degrees Celsius) of the metal block? (The specific heat capacity of aluminum, CsAI, is 0.903J/(g °C).) Express the temperature in degrees Celsius to two significant figures Submit My Answers Give Up

Explanation / Answer

part B

mwater*s*DT = m*s*DT

0.48*4.18*(25-0)+(0.48/18)*6.01*10^3 = 55*0.903*(x-25)

final temperature of Al = 29.23 C

part A

q absorbed = 62*2.03*(0+18)+(62/18)*6.01*10^3 + 62*4.18*(25-0)

   = 29.445 kj

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