Question

Heat of Vaporization and Heat of Fusion Learning Goal: To calculate the total energy required to convert a solid to a gas using heat capacity, heat of fusion, and heat of vaporization. The amount of heat required to melt one mole of a solid is called the heat of fusion (ΔHfus). The amount of heat required to vaporize (boil) one mole of a liquid is called the heat of vaporization (ΔHvap). The heat of fusion and the heat of vaporization can be used to calculate the amount of heat needed to melt or vaporize, respectively, a given amount of substance. For example, the heat of fusion for H2O is 6.02 kJ/mol, which means that 6.02 kJ of heat is needed to melt a mole of ice. Twice as much heat is needed to melt twice as much ice, as shown here: 2.00 mol×6.02 kJ/mol=12.0 kJ

Constants Heat of fusion (ΔHfus) is used for calculations involving a phase change between solid and liquid, with no temperature change. For H2O, ΔHfus=6.02 kJ/mol. Specific heat capacity (C) is used for calculations that involve a temperature change, but no phase change. For liquid water, C=4.184 J/(g⋅∘C). Heat of vaporization (ΔHvap) is used for calculations involving a phase change between liquid and gas, with no temperature change. For H2O, ΔHvap=40.7 kJ/mol. Part A How much heat is required to melt 52.5 g of ice at its melting point? Express your answer numerically in kilojoules. 17.5   kJ   SubmitHintsMy AnswersGive UpReview Part Correct Part B How much heat is required to raise the temperature of 52.5 g of water from its melting point to its boiling point? Express your answer numerically in kilojoules. 158.0775   kJ   SubmitHintsMy AnswersGive UpReview Part Incorrect; Try Again; 4 attempts remaining; no points deducted ****NEED HELP PLEASE PART B ANSWER IS WRONG****

Answer 1

q = m c dT       -- equation 1   

Where, q = heat change                                                 , m= mass in gram,

c = specific heat (in terms of J/gK)                     

dT = final temperature – initial temperature.

Part B. Given,

                Mass of water = 52.5 g

                Initial temperature of water = 0⁰C             [Melting point]

                Final temperature of water = 100⁰C          [Boiling point]

                dT = 100⁰C – 0⁰C = 100⁰C

                Specific heat = 4.184 J/g⁰C

Putting the values in equation 1

                q = 52.5 g x (4.184 J/g⁰C) x 100⁰C

                or, q = 21966 J   = 21.966 kJ                                          ; [1 kJ = 1000 J]

Therefore, the amount of heat required to raise the temperature = 21.966 kJ