[peak]

Question 1

Calculate the value of Go for the formation of 1 mol of phosphorus trichloride from its constituent elements:

P2(g) + 3 Cl2(g) ---> 2 PCl3(g)

My attempt:

1. I first solved for ∆H using ∆H = ΣHf (product) - ΣHf (reactants)
2. I solved for ∆S using ∆S = ΣSf (product) - ΣSf (reactants)
3. I solved for ∆G using ∆G = ∆H - T∆S. I wasn't sure what temperature to use but I used 298K since I retrieved the thermodynamic quantities from a website that got its quantities at 298k.

I didn't get the correct answer. At first, I tried using 1 mol of PCl3in the ∆H and ∆S equations but it was still incorrect. I then tried using 0.5 moles of P2, 1.5 moles of Cl2 and 1 mole PCl3 in the ∆H and ∆S equations since it asked for the formation of 1 mole of PCl3, but these quantities also gave me an incorrect answer. I'm not sure if I'm over thinking it since it looks fairly simple haha, but I hope you guys can clear things up.

Question 2

When a reaction was carried out in a bomb calorimeter 17.50 kJ of heat was released. If the initial temperature was 22.418 C and the total heat capacity of the system was 17.68 kJ °C-1. What is the final temperature ?

My attempt:

I tried using q = MC∆T but is there insufficient data? Since I couldn't figure the mass or the change in temperature.


Thank you

[fledarmus]

What website did you use for your thermodynamic values, and what were the values that you used? Did you take into account the state of the substances when you chose your values?

[peak]

http://bilbo.chm.uri.edu/CHM112/tables/thermtable.htm is the site I used. I'm fairly sure the values I chose are for the correct state.

These are the values I used:

P2(g)
∆H = 146.2 kJ/mol
∆S = 218.0 J/mol·K

Cl2(g)
∆H = 0 kJ/mol
∆S = 223.0 J/mol·K

PCl3(g)
∆H = -287.0 kJ/mol
∆S = 311.7 J/mol·K

Note* Question 1 is suppose to say "Calculate the value of ∆G" not "Go". Sorry for the typo.