Log in

View Full Version : Enthalpy change, first ionization energy, determine "n", boiling point, vapour press.


kaylaxx832
Nov 25, 2007, 11:02 AM
Hey guys, I have about 8-9 questions, so I'm going to cut it down to about 4 per post. I'd appreciate any help that I can get, I have these sample problems, but no answers or workings, and my exam is tomorrow.

1. When 5.00 mL of a 0.60 M solution of a tribasic acid H3A(aq), is reacted with 45.00 mL of 0.20 M NaOH(aq), both at 26.0*C, the final temperature of the combined solution is 28.0*C. Assuming the volumes of the solutions are additive, and the density of the final solution is 1.10 g/mL, calculate the enthalpy change for the reaction in kJ/mol of H3A. Assume the heat capacity of the solution is the same as water.
H3A(aq) + 3NaOH(aq) --> Na3A(aq) + 3H20(l) deltaH = ?

2. Calculate the first ionization energy of atomic hydrogen from the following data:
H2(g) + Cl2(g) --> 2HCl(g) deltaH* = -184.62 kJ
H2(g) --> 2H(g) deltaH* = 435.94 kJ
Cl2(g) --> 2Cl(g) deltaH* = 243.36 kJ
Cl (g) + e- --> Cl-(g) deltaH* = -348.79 kJ
H+(g) + Cl-(g) --> HCl(g) deltaH* = -1395.38 kJ

3. A ground state hydrogen atom can absorb light of wavelength 93.8 nanometers. Determine the value of n for the excited state.
Rh = 2.179 x 10^-18 J En = - Z^2 x Rh
n^2


4. Calculate the vapour pressure above a solution made by mixing 321 g of toluene, C7H8 (92.15 g/mol) with 398 g of benzene, C6H6 (78.12 g/mol) at 60*C. At 60*C, the vapour pressure of pure toluene is 140 mmHg and the vapour pressure of pure benzene is 396 mmHg.


5. A solution is prepared by dissolving 31.65 g of NaCl in 220.0 mL of water at 34.0*C. Calculate the boiling point of the solution assuming complete dissociation of NaCl. The density of water at 34.0*C is 0.994 g/mL, the boiling point of water is 100.0*C and Kb for water is 0.51 *C kg/mol.


Thanks for any help you guys can offer, and please check out my other post with a couple of more questions.

PLEASE NOTE: This isn't a homework question, I just really need to figure it out before my test, just in case it shows up! :)