# [SOLVED] Heat sublimation ? not in my book or anywhere online

Heat sublimation ? not in my book or anywhere online

The standard heat of formation of PI3 (s) is -24.7 and the bond energy in this PI molecule is 184 . The standard heat of formation of P (g) is 334 and that of I2 (g) is 62 . The I2 bond energy is 151 .

Calculate the heat of sublimation of .

PI3 [PI3(s) --> PI3 (g) ]

not even in my book or not talked about in class but somehow is given as a hw problem go figure

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## This is the best answer for Heat sublimation?

_____I answered this Q before. You said I was wrong; maybe you can tell me why. Did you use the sum of the eqns? I did and they do give the right answer. If you use the ~value I supplied, that was about right, then you got the wrong answer; I expected you to do the math. I also gave a ref of what the answer should be; (the sum of the dHs just might NOT give that number within 1%!

to 1st approximation: heat sublimation of PI3 ~ (MW PI3 / MW I2) * heat sublimation of I2.

I have given the answer below, again.

_____Bond energy and enthalpy combination and HESS

_____1/4P4(s)-----------------> P(g)_______dHvap = 334 kJ/mole P

___3/2 * [I2(s) ------------------> I2 (g)]_____dHvap = 3/2 * 62 kJ/mole I2

_____P(g) +3/2 I2(g)---------> PI3(g)____dHrxn= - [(3 bonds*184) - 3/2 bonds*151]kJ/mole

sum eqns and dHs above

_____1/4P4(s) + 3/2 I2(s) ---> PI3(g)_____dHf PI3(g) = sum dHs = ?? kj/mole

_____PI3(s) --------> 1/4P4(s) + 3/2 I2(s)__-dHf PI3(s) = 24.7 kJ/mole

sum eqns and dHs for these two reactions

_____PI3(s) --------------------> PI3 (g) ___________dHsubl = ??

SOLVE (answer should be ~ 95 kJ/mole; not ~400 kJ/mole)

Basic mathematics is a prerequisite to chemistry – I just try to help you with the methodology of solving the problem.

22 hours ago

Source(s):

0.98 eV heat of sublimation of PI3 = 94.56 kJ/mole

1 eV = 96.48530891 kJ / mole (wikipedia)

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Do the thought experiment:

Take it apart into the component elements

vaporize those elements

recombine them to PI3(g)

The total energy change of this will be the heat of sublimation.

I think this is the correct answer for what is Heat sublimation?
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if "the bond ability in this PI molecule is 184", for in line with mole of P_F bonds. then the reaction is 3X's 184kJ: (A) PI3 (g) --> P(g) & 3 I(g)..... (+552kJ) "The I2 bond ability is 151 " m for the reaction: (B) I2 (g) --> 2 I (g) ..... (+151kJ) "the huge-unfold warmth of formation of PI3 (s) is -24.7", for the reaction: (C) P(s) & a million.5 I2(s) --> PI3 (s) ....(-24.7kJ) "the huge-unfold warmth of formation of P (g) is 334", for the reaction: (D) P(s) --> P(g) .... (+334 kJ) "the huge-unfold warmth of formation of I2 (g) is sixty two", for the reaction: (E) I2 (s) --> I2 (g) ... (+sixty two kJ) ==================== Calculate the warmth of sublimation of : PI3(s) --> PI3 (g) could be stumbled on by utilising, the opposite of equation (C), to supply PI3 (s) as a beginning cloth the opposite of equation (A), to supply PI3 (g) as a product -(C) : PI3 (s) --> P(s) & a million.5I2(s) ....(+24.7kJ) -(A) : P(g) & 3 I(g) --> PI3 (g) ..... (-552kJ) then to calcel out undesireables: +(D): P(s) --> P(g) .... (+334 kJ) cancels out P(s) & P(g) +a million.5(B)'s: a million.5 I2 (g) --> 3 I (g) ..... (a million.5)(+151kJ) cancels out I(g) & I2(g) ============== hess's regulation says that if combining equations -A , -C , +D , & a million.5B can supply the equation which you go with... then combining the flexibility from -A , -C , +D , & a million.5B can supply the flexibility which you go with... (-dHA of +24.7) & ( -dHC of -552) , +dHD of 334) , & (a million.5dHB of 151 = 226.5) = your answer: 33.2 kJ you would be able to desire to contemplate rounding off for sig figs to dH = 33 kJ, through fact a lot of your dH's weren't measured to the 0.1th of a kJ

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