No Questions on Whatsapp please.

I will no longer answer Q’s on whatsapp. Replying on my phone takes too much time. Ask questions here.

I will answer them on this blog. Pleease identify yourself, so I can focus on KYUEM students.

 

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9 thoughts on “No Questions on Whatsapp please.

  1. Hello , Mr Allan. For enthalpy change of formation, we use S instead of S8. I thought for the standard form, we need to choose the most stable one. But why S is more stable than S8? How about for Phosphorus? We use P or P4 for formation? Thank you.

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    • It should be S8. But we cheat…. We could easily write 1/8 S8 which would give “1S”, but to make it short, we just write S. It doesn’t seem to cause any problems but doing this, and balancing equations with just “S” in them is easier.
      We sometimes do the same with phosphorous, but for some reason it’s more common to put the fraction in, i.e. 1/4 P4.
      And of course, you’ll be fmiliar with the use of 1/2’s for diatomics like H2 and O2.
      S is of course unstable having an unfilled octet and two unpaired e-. S8 is much more stable. But when we wrote jus the “S”, we assume it’s understood taht we are indeed talking about 1/8 S8.

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  2. What is meant my “low volatility”
    It can be described in a number of ways:
    @ A substance that does not vaporise much.
    @ A substance that produces a small vapour pressure
    @ A substance (usually a liquid) that has weak intermolecular forces.

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  3. Sir, for H nmr right, would there be any difference in the peaks produced if a substance in D2O solvent was then dissolved in CDCl3?

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    • Hi. Sorry I misunderstood your question when I saw you earlier.

      The D in CDCl3 does NOT break off, so it cannot replace the ‘labile H’ in other organic molecules (-OH, -COOH, -NH2 groups)
      So if you ONLY added CDCl3 then ALL peaks would be present; No peaks would disappear. CDCl3 is used only as a solvent. The “D” in it is to stop a “solvent peak” appearing on top of the spectrum of the compound we are analysing.

      the D in D2O does beak off and can replace labile H.

      So YES, your spectra would be different.

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  4. Salam sir, for the definition of electron affinity, would it be wrong if I used ‘an’ atom/ion instead of ‘1 mol’ of atoms/ions ?

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    • You can talk about one atom, but at the end you need to scale it up to molar quantities. The IE values are in kJ/mol yes? So you can’t completely avoid talking about a mole.
      You could say something like “The energy per mole required to remove one electron from one gaseous atom”
      but that sounds slightly silly.

      Best say something like “The energy requited to remove a mole of electrons from a mole of gaseous atoms to produce a mole of singly charged ions” which is the usual way of saying it.

      Sometimes conformity is good.

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