Per Solve each of the following calculations. 1. How much heat energy is require

Question

Per Solve each of the following calculations. 1. How much heat energy is required to melt 15 g of ethyl alcohol at its melting point if the Hf = 105 J/g? 2. How much heat energy is required to vaporize this same amount of ethyl alcohol if the Hy-41.7 kJ/mol? The formula of ethyl alcohol is C2HsOH llo Hog 3. Account for this difference between the energy needed to vaporize and the energy needed to melt. Which energy is greater? 4.1 What is the heat of vaporization of a substance if it absorbs 75 kJ of energy to completely vaporize 2.1 mol of the substance at its boiling point?

Explanation / Answer

1)
Hf = 105 J/g
m = 15 g
Heat required, Q = m*Hf
    = 15 g * 105 J/g
    =1575 J
Your units are wrong thats it
2)
number of moles, n= mass / molar mass = 15 g / 46 g/mol = 0.33 mol
Hv = 41.7 KJ/mol
Heat required, Q = n*Hv
     = 0.33 mol* 41.7 KJ/mol
     =13.761 KJ
      = 13761 J
Again your units are wrong. Thats it
3)
Energy required to vapourise is greater
By 13761 - 1575 = 12186 J

4)
Hv = Q / number of moles
     = 75 KJ/2.1 mol
     = 35.71 KJ/mol

You have done this one wrong. You need to divide and not multiply

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