g'chem q
Started by dat_student
dat_student said:
my best guess would be 1 cal, since that's what it takes to heat 1 degree, so reduction by that much releases 1 cal to the environment...thanks DAT student for making me question my studying...again.
mybaa said:
you're very welcome but wrong answer 🙂
mybaa said:
wrong again 🙂
mybaa said:
3
mybaa said:
u tried for 5 min, so impatient
Quit playing dat student, anyody knows that 5mins on a question like that is NOT GOOD (try spending 5 mins on each DAT question and tell me how you do). Could you tell us how to do it or are u going to be a pain? Besides what kinda answer is 3. Didn't ur teachers tell you to always put units with ur answers. 3! 3 what? cows? I'm just pulling ur legs but yeah, i'm getting frustrated too. 🙂
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duh? said:
oop! sorry. 3 kj/mol
dat_student said:
Duh...what Mr. DAT student did not give us is the enthalpy of hydration and Lattice enthalply for salt dissolved in water, which is 784KJ/mol, and 787KJ/mol respectively. Now you find the number of moles of NaCl, and then find the final Lattice enthalply and enthalpy of hydration. Lattice enthalply, btw is the solute-solute bond breaking, and enthalpy of hydration is solvent-solvent breaking + solute-solvent forming. The number of moles of NaCl for this is close to 1, so, we can just subtract enthalpy of lattice-that of hydration to land at a grand number of 3KJ/mol.
To😀AT student, I know u wanna give others a try, but if u do post a question, can u post a workout answers too, cuz many ppl will be fustrated and won't be able to do anything if they don't understand this one...at least it happens to me. Thanks
mybaa said:
ADA won't tell you the correct answers for the real DAT. 🙂
SIDE NOTE: Some parts of your last argument are not true.
duh? said:
I had no idea. Thanks for helping me find the answer.
mybaa said:
no other info (lattice, enthalpy etc) was needed. simply divide the number by 1/3 mole of NaCl, 1 / (1/3) = 3 kj/mole
dat_student said:
Again, where did you get "the number" from? I assume that would have to be 1 kj, and I don't see that anywhere in the problem...
Flipper405 said:
(m*c*delta temp) gives you "1"
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dat_student said:
hey, I don't think doing m*c* change in T works as u want it to in this case...doing 4.18 * 250G * 1 degree change does give 1045 J, which is around 1 KJ, but the addition of salt does change the specific heat capacity, in which case this does not really work out the way u want it to. those r my 2 cents, let me know what u think.
I think, (i) wont change delta H it will only effect the coligitive properties.mybaa said:
mybaa said:
NaCl was not added to a salt solution. We want to know the heat as a result of adding NaCl. Finding just the heat is meaningless. So you have to find "heat per mole."
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