user103816

I meant criss-cross method is true for all ionic compounds but not for all covalent compounds( For some covalent compounds this method works).

What I want to say is that I think criss-cross method is only applicable to ionic compounds only.

How about $C_2H_2$ any many others like this. We cannot apply criss-cross rule in genral. Suppose we know we have some compound made up of $C$ and $H$ then we will apply criss cross rule to get $CH_4$! which is can be wrong if the compound $C_2H_2$. So this method should be true only for ionic compounds not colvalent compounds.

How criss-cross rule applies to $H_2O_2$?

Please explain in detail in your answer. If we are interested in the least unit that is repeated again and again to make the whole material then consider $H_2O_2$ , in $H_2O_2$ the least unit is $OH$ but actually the whole molecule is $H_2O_2$ not $OH$.

I am asking in general for all compounds like molecules. While applying criss-cross rule for any compound we divide the oxidation numbers with their gcf, why?

Could you explain why we divide the oxidation numbers with their gcf.

It appears your answer is right. $As$ should have $-3$ oxidation state. I am quite confused with the the book that I have already mentioned in which $As$ makes 5 bonds. Let's come to my present question. Does this method works for purely covalent compounds? If the diff. b/w electronnegativities of the constituent atoms is very less then would it be approriate to talk about oxidation states? Would we use valancy in that case?

If all the bonds are equivalent the coordinate bond should be identical with the usual covalent bond. Shouldn't all the equivalent bonds cause same oxidation states? How can two identical types of bonds be different in some way. I have another doubt(Excuse me for this , I am not in touch with chemistry from some years) Would the hybradysation occurre? If yes then all the bonds will be exactly equivalent, that is the electron pair in the coordinate bond will be exactly at same distance from $As$ as the usual covalent bond(in which both As and Ga share 1-1 electron).

If GaAs crystal contains two different type of bonds then will the electrons corresponding to the two different types of bonds have different band gaps. I am familiar with the 1.46eV band gap energy of $GaAs$. What is the band gap energy of the electrons in the coordinate bond?

Note that the text also writes:"...one of the four covalent bond is formed by the $As$ atom contributing two electron( coordinate-bond), while the $Ga$ atom contribute none...". This implies that $As$ on an average does not have $-3$ oxidation state.

Mannaia, chemistry.stackexchange.com/questions/9317/….

Soory I meant changing resolution keeping same width in px in photshop.

can you confirm this by actually resizing and saving image in retina laptop e.g. apple mac book?

Would Photoshop behave similarly on retina display computers? E.g. consider a 2dpr laptop. Would changing resolution in Photoshop keeping width in px intact not change size in mega bytes?

If I have two images 600 photshop px wide one with reolution 72px/inch another with 36px/inches both have same size in mega bytes. Which means photshop doesn't change physical px in an image.

I guess that when we say Earth moves from west to East, we mean the land surface not the planet Earth. Now East and west of a surface are obviously directions not the hemispheres.

@ymirsson I know that each surface point moves towards its east. But the Earth doesn't move towards its east because the Earth as a whole doesn't have any East or west; it has Eastern hemisphere and northern hemisphere.

@ymirsson What is East of Earth? Does it mean East of the rotation axis?

@PolyGeo Thanks for guiding me.I've asked the question there earthscience.stackexchange.com/q/7405/5344 and I've also removed my speculation part.

@ymirsson But in that image too the eastern hemisphere can be seen to move towards western hemisphere. And that is my main question.

Well. May be it's a question of Geodesy. May be it's not. But that is what I read in my Geography book. So that's a geography question for sure. I don't know a particular SE site for geography. If there is then I request to migrate my question to the most appropriate site.

@Vince If removing my speculation part makes the question a better fit for SE philosophy then I have no problem in removing that part.

@Kersten to your 2nd comment. When we say Earth rotates from west to east we don't say a point on earth moves from its west to its east. We just say Earth moves from west to East. Now what is west and East for Earth? My knee-jerk is that Earth's west means the western hemisphere. Then it is not wrong to say Earth moves from East to west as the Eastern hemisphere always move towards the western hemisphere.

@Kersten I think for explaining why Sun rises from East we even don't need to take any reference because the north pole is already well defined. By knowing North of any point we can know it's east, west and south. Then for every frame of reference any point on earth will always move towards it's east.

I guess I can understand things now. If I'll have some major doubt I'll comment on your answer. Thanx for explaining.

perhaps there is only a unique least positive r for both -1 mod 9 and 8^33 mod 9.

PErhaps I got why the polynomial division is working. But still I'm somewhat confused about 8^{33} is equivalent to (-1) because their difference is divisible by 9. No how do we know that -1=9k+r= 9(-1)+8 and r=8 gives the same r we want.

hmm perhaps we are just writing 2^{99} in a form of 9k+r

The degree will be 0. But still it is the remainder of Polynomial division not Euclid division.

Yes I understand that.

I got another doubt. Why is the least positive remained of $8^{33}/9$ is same as least positive equivalent remainder of $-1 \bmod 9$. I come to the polynoimial doub first...

Hello.

I know that. In our case the remainder of polynomial division a numeric constant. But why is this constant same as would be the remainder of actual Euclid division performed on actual numbers. BTW I could not understand which degree of denominator are you saying in Euclid division.

but if $q(c)=0$ then $r(c)$ is actually the remainder but still the remainder of polynomial division. How can we show that if q(x) has a degree 1 in x then r(c)[which will obviously be a numeric constant] is same as would be the remainder of Euclid division?

I also don't get how can the remainder be negative in numerical division, e.g. 33/5 gives remainder 3(i.e. 33-5*6) but if we do 33-(7*5) then we get (-2) as the remainder. But then why does it make sense? Why do 3 and -2 become congurent and help in simplifying calculations?

Aren't Polynomial remainder theorem and Euclid division algorithm different? In polynomial division we subtract powers of $x$ and if the divisor's degree is higher than $2$, say divisor is $x^2+1$ then the remainder will be of type $ax+b$ which exclusively depends upon $x$.

@Mithoron If Na+ and Cl- are supposed to be at infinite distance and then accelerated towards each other then in the first collision how much energy will be evolved? Will that energy of one collision be exactly equal to the bond energy?

@Mithoron *I you'd have unbound Na+ and Cl- and they attracted each other, they would collide and get bound * . Wait. When they will be attracted whole of the Potential energy will be converted into Na+ and Cl+'s K.E. Now when they will collide they will for sure get separated again because the energy needed for that is initial P.E. which can be given by the K.E. But this may not happen if the collision is inelastic.

@Mithoron I don't know the concept of Enthalpy and Entorpy. Could you explain in simple language? E.g. could you explain the example of NaCl?

@Mithoron Are you there?

Hello.

@Mithoron No, I am not aking why force exists.

@Mithoron That's exactly what my question is. Why should Enthalpy decrease and entropy increase?

@Mithoron This is what I was told by many chemistry teachers when I was a student. They also told be that lesser energy --> More stability. And every thing in nature wants to be more stable. Although I never quite got their 'nature' arguments, like XYZ chemical reacts in a particular way because of its nature etc etc.

You mean spelling, ah my bad.

Do you remember anything else which came from our discussion? I remember, 1) use of ever and even. 2) one-time or continues.

Perhaps he can use "Don't you even bath". But to me there is a difference b/w the sense it conveys-- which I can't explain in English. I think we should stop chatting and add these particular points on main site.

"Don't you ever bath", here 'ever' conveys a specific sense. It is well known that everyone should bath and they do bath. I should bath everyday. If I tell someone that I never bath, he'd reply "Don't you ever bath! WTF!. ?He can't use "Don't you **even ** bath".

I am trying to understand the difference between the use of 'even' and ever'. They give different sense to the sentence.