Question

Question Part Submissions Used Mercury has the following physical properties: normal melting point = -39°C, normal boiling point = 357°C, heat of fusion = 2.33 kJ/mol, heat of vaporization = 284 J/g, specific heat = 0.139 J/g·°C. Calculate ΔH for the conversion of 171 g of solid mercury at its freezing point to mercury vapor at its boiling point. Note that the heat of vaporization is in atypical units of J/g. To calculate that value, simply multiply so that units cancel to give J.

Answer 1

moles of mercury = mass/ molar mass = 171 / 200.59 = 0.8525

Heat required to melt solid mercury = moles x heat of fusion = 0.8525 x 2.33 = 1.9863 KJ = 1986.3 J

heat required to raise temp of liquid mercury from -39 to 357 = specific heat x temp change x mass

                   = ( 0.139 ) x ( 357 -(-39)) x ( 171 = 0.139 x 396 x 171 =9412.5 J

Heat required tovaporise = heat of vaporisation x moles = 284 x 0.8525 = 242.11 J

Total heat required = sum of three heats = 1986.3+9412.5+242.11 = 11640.9 J = 11641 J