« first day (1387 days earlier)   

12:07 AM
Well bye guys, g'night
 
G'night @Mithoron
 
1:03 AM
would "Why is the Delisle temperature scale 'backwards'?" be a good question for this site?
 
Jan
What is the Delisle temperature scale?
 
The Delisle scale (°D) is a temperature scale invented in 1732 by the French astronomer Joseph-Nicolas Delisle (1688–1768). Delisle was the author of Mémoires pour servir à l'histoire et aux progrès de l'Astronomie, de la Géographie et de la Physique (1738). == HistoryEdit == In 1732, Delisle built a thermometer that used mercury as a working fluid. Delisle chose his scale using the temperature of boiling water as the fixed zero point and measured the contraction of the mercury (with lower temperatures) in hundred-thousandths. Delisle thermometers usually had 2400 or 2700 graduations, appropriate...
 
@Ixrec maybe. You could also try hsm.stackexchange.com
 
Jan
I would say no. Physics or hsm.
 
HSM makes sense, thanks
 
1:10 AM
@Ixrec is that an offshoot of the Fahrenheit discussion in Mos Eisley?
 
that is what got me browsing Wikipedia articles on temperature scales, so I guess so
 
:-)
 
1:22 AM
What's HSM stackE?
Oh okay nevermind found it
 
Jan
@getafix Istry of signs and mafs ;)
 
Yeah found it :). How goes @Jan?
 
Jan
Excuse the terrible pun, but my answer is 'off to bed' ^^' (It's half two in the morning here D=)
 
I still don't understand all that well =/
I am so screwed for my assignment :P
 
@Jan 'night then
@WDUK what don't to understand?
 
1:37 AM
i have two molecules that i have to determine if they form a covalent or ionic bond, then also have to explain why they have different melting temperatures
for room temp at 1 atmospheric pressure
i could google what their bonds are but i wont fundamentally understand how to work it out myself which bothers me greatly
 
I see.
 
safe to say i won't be doing second year after this
 
Okay. So a bonds ionic character is a) determined by the diff. In electronegative of the participating species.
But it's not the simple. You need I check somethings else too
 
well see the book never mentioned that term "electronegative"
at any point
 
1:42 AM
what values are considered high/low ?
seems to range from 1 to 3
 
I don't know if there's a more modern formulation that replaces Fajans rules but they work well
Electronegativity values are tabulated read up on the Pauling scale
 
so from that wiki
Al3 S2 would be ionic
because it would be Al+3 and S-2
giving only +1 charge
or am i confusing two seperate things
 
Be right back, sorry doing something
 
no probs :)
 
 
1 hour later…
3:14 AM
So yeah coming back. I would expect it to have ionic character..,saying something is really completely covalent or ionic (or so I've been told) is hard
If you look it up some data..it has a melting point of 1370 K
In its crystal str. the sulphide ions form a hcp lattice and Al occupies the tetrahedral holes.
The main idea is a) if the difference in electronegativities is large then bond is ionic
b) if the anion is large, and it's electron clouds are polarisable..you get more covalent character
 
4:16 AM
@getafix Oh, it is I who am the dense one. (0: I should read more. I see. When Cl meets a Br salt in solution, it seeks to supplant Br- and become Cl-, and this makes the whole solution warmer.
 
so can it be correctly said that in the compounds where the ions are similar in size are the least covalent ?
 
I wonder if it could be said that two lovers of Japanese animation have a kawaii bond. If one loves animation more, then it's polar kawaii bond.
 
4:38 AM
@Abhirikshma As far as I remember, if the electronegativity difference between two atoms is more than 1.4, it's an indication that the bond is closer to ionic. The less the difference, the more covalent the bond is.
 
 
2 hours later…
 
1 hour later…
7:26 AM
@CopperKettle yes
@Abhirikshma electronegativities and polarisability. Read with wiki on Fajans rules I posted that a while ago..scroll up and you'll see
 
 
3 hours later…
10:55 AM
in Tavern on the Meta on Meta Stack Exchange Chat, 2 mins ago, by IͶΔ
Though we already have a bot in chem that detects dupes.
CC @Mith
 
11:07 AM
-4
Q: PLEASE HELP IMMEDIATELY

IsaacThe tea with sugar added in the first problem begins to cool. You notice that the tea begins to get cloudy and a white powder begins to form on the bottom of the cup. What is happening and why does this process occur?

I wonder how many downvotes can there be on a question.
 
11:24 AM
@IͶΔ I'd be willing to take bets and start a pool..i reckon ten to fifteen min.
I found it funny that you guys did not even link to the hw policy..and just went is this for real Loool
 
 
1 hour later…
12:24 PM
@IͶΔ :D
 
12:37 PM
 
12:51 PM
Hahahaha
:D
 
1:19 PM
"That last LinkedIn request set a new record for the most energetic physical event ever observed. Maybe we should respond." "Nah."
2
 
 
3 hours later…
4:27 PM
2
Q: Chemistry — Top User Swag!

JNatWe want to congratulate and thank everyone that helped this site and community grow healthily into what they are today! If you can find your name among the top 72 users in the first two pages here, we have a surprise for you! Hoping to get a reaction with that joke... (。ˇ艸ˇ) We want to se...

 
@Feeds :OOOOO
 
5:18 PM
hi. I am trying to numerically integrate and the spectral overlap integral using the trapezoidal rule. However, I think the units gets messed during the approximation. The integral is $\int F(\lambda) \epsilon (\lambda) \lambda^4 $. So, if the wavelength is in m, and the molar absorption coefficient is in m^2/mol, the integral should come out in m^6/mol. However, looking at the trapezoidal rule:
$J (\lambda) \approx \frac{\lambda_{i+1} - \lambda_i}{2} \left[ F(\lambda_i) \epsilon_i \lambda_i^4 + F(\lambda_{i+1}) \epsilon(\lambda_{i+1}) \lambda_{i+1}^4 \right]$
wow, mathjax not working in here, apparently
anyway, factor (b-a)/2 at the start of the approximation, should be in units of meters, right? So the integral units become m^7/mol, and not m^6/mol. How go around this?
 
 
2 hours later…
7:12 PM
woooo swag
 
 
3 hours later…
9:47 PM
@skullpetrol ⚆ _ ⚆
 

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