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My first chemistry test ever

  1. Oct 8, 2008 #1
    It's not exactly homework, as we've already finished the test, but I'm posting it here anyways. I've verified that I got most of the questions right, but there are still some I'd appreciate some input on. Warning: This is easy chemistry. By the way, the test was given in Norwegian, and I am a little unsure about the names of certain bonds and other chimcal things in English, but I'll try, and I hope you understand it.

    So here we go. First:
    We were asked about "three main kinds of chemical bonds". What kinds of bonds are the main ones? We were also told to use the term "electronegativity" in our description.

    Secondly:
    We were supposed to find the chemical names and the trivial names of a few substances. I've done this, and got them correct, but then the task asks for the ions in the substances that are ionic bonds. Which of these are ionic bonds, and which are not? And why?
    Na2O, HCl, CaCO3, H3PO4, Mg(NO3)2

    And then we were to explain how we find the formula of the product when two chemical elements react. I know how to do it, and I've done all the tasks correctly, but I feel that my explanation was rather weak. How would you have put it?

    Thanks a lot for all replies!
     
  2. jcsd
  3. Oct 8, 2008 #2

    GCT

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    Hi , you need to state your own explanation and then we can move forward from there.
     
  4. Oct 8, 2008 #3

    symbolipoint

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    Your answers to "Secondly" can in part be found from a good introductory level or elementary level textbook; maybe also from some old industrial chemistry textbook. Cement and hardware related references will yield a couple of the common names. The chemical names should seem obvious and the instruction for doing this is plainly supplied in a sensible Chemistry course at the introductory and elementary levels. One strange item to answer is the common name of Na2O. Does it really exist in practice, or only under carefully controlled conditions? Anyhow, the name for it is easy to derive. (I could give the names for most of those in this list, but the system or administrator would give me another warning or maybe something worse).

    For the part "First", if your textbook does not give enough plain information, then you need a better or different book. Either an atom takes up the free electron(s) or it gives up free electron(s). Which kind of bonding is associated with those situations? If atoms or groups share electrons, then this is another kind of chemical bond, which is called What? I can think of one more type of chemical bond, and my hint is the word, 'chelation'. I'm actually a little unsure about this third type of chemical bond but using my best educated judgement.
     
  5. Oct 9, 2008 #4
    Well, for the first part, the book didn't state clearly what bonds are the main ones. I answered "covalent bond, polar covalent bond and ionic bonds", and wrote nearly one page to describe it. My friend didn't even know what electronegativity was, but wrote "metal bond, covalent bond and ionic bond", as the book says there are three strong bonds and 2 weak bonds, so he assumed that the strong bonds were the main one. But it doesn't say anything about "main bonds", or the strong bonds being more "main" than the weak ones, if you know what I mean, so I got confused.

    Secondly: I don't know if there's a common name to Na2O, but the others have got it, at least in Norwegian. But after me and two friends have been reading through the book several times, we still can't decide which of all of the substances are ionic bonds. Some of them are clear, like Na2O, but we have trouble deciding wether the others are ionic bonds, f.eks. Mg(NO3)2.

    As for number three, I wrote that all atoms "wants" to have 8 electrons in their valence shells, except for H and He, which "wants" two (full K-shell, that is). So we just find out how they "co-operate" to make everyone happy. And we must also note that some gases, like N, O and H, normally appears in pairs, f.ex. O2 in stead of O.

    I have already delivered, so I don't remember exactly what I wrote, but it was something like that. When I do tasks, I do it quite naturally, logically, so it was hard for me to put it down in words. I think it was a quite weak explanation. But I know quite a lot of my friends forgot that thing about gases. F.ex. in the task, we were to find out a balanced equation for K + O. Most people just wrote K+O -> K2O.

    As I've written, this semester is our first with chemistry, so it's very basic chemistry we're doing. But I appreciate all help, so thanks a lot.

    Thanks for you replies
     
  6. Oct 9, 2008 #5

    symbolipoint

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    Your choice of "polar bond" seems like a good one, although this is probably very different than the other one I was describing (with my hint of "chelation"). With further thought, I believe "polar bond" is one of the correct choices.
     
  7. Oct 9, 2008 #6

    Borek

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    Not sure what you mean by "common" name. This is sodium oxide (not to be mistaken with peroxide NaO and superoxide NaO2).

    This one is ionic, but there is nothing clear nor obvious about that - most oxides are covalent.

    This is salt - magnesium nitrate. Salts are ionic in general. This one is made of two ions - Mg2+ and NO3-. "Internal" bonds in NO3- are not ionic.

    These are called diatomic molecules.
     
  8. Oct 9, 2008 #7
    Thanks for all the replies!
    In Norwegian, we learned about chemical names and trivial names of substances. One of the above called it a common name so I adopted this term. F.ex. HCl is called "hydrogenklorid" as a chemical name in Norwegian, but it has also got a trivial name, "saltsyre" (salt acid) in Norwegian. Don't know what it's called in English, but I would guess you have something like it. So I guess "sodium oxide" is what we were looking for here, but we've never heard of it in class, so I guess (hope) it wasn't all that important.

    Again, thanks for your views. About the explanation of the octet rule and that, what more could I have added?

    And by the way, would that mean that Na2O, CaCO3, H3PO4 and Mg(NO3)2 all are ionic bonds, while HCl is the only substance not an ionic bond? Or am I wrong again?

    Thanks
     
  9. Oct 9, 2008 #8
    All of the substances you named have ionic bonds (between ions), but the complex ions such as CO3, PO4, and NO3 have covalent bonds within themselves.
     
  10. Oct 9, 2008 #9

    Borek

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    HCl is covalent.
     
  11. Oct 9, 2008 #10

    chemisttree

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    Did your book describe metal bonds, covalent bonds, ionic bonds, hydrogen bonds and dative bonds?
     
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