posted by Trish on .
Calculate the energy that must be removed to convert substance X from a gas at 115°C to a solid -50.7°C. Assume X has a molar mass of 75.0 g/mol.
Specific heat capacities
ΔHvap 20. kJ/mol C(s) 3.0 J/g · °C
ΔHfus 5.0 kJ/mol C(l) 2.5 J/g · °C
bp 75°C C(g) 1.0 J/g · °C
If you can go step by step so I can understand how this is done That would be great! Thanks
You must know how many grams or how many moles you have initially. If moles, ok. If mass, convert mass to moles.
q1 = heat removed to move from 115 C to b.p.
q1 = mols x specific heat vapor x (Tfinal-Tinitial).
q2 = heat removed to convert vapor to liquid.
q2 = moles x heat vaporization.
q3 = heat removed to move from b.p. to melting point.
q3 = moles x specific heat liquid x (Tfinal - Tinitial).
q4 = heat removed to freeze liquid at m.p.
q4 = moles x heat fusion.
q5 = heat removed to move from m.p. to -50.7.
q5 = moles x specific heat solid x (Tfinal-Tinitial).
qtotal = q1+q2+q3+q4+q5