Since I’m seeing chem questions pop up on the awesome new forum, I’m recreating the old chem questions thread. Just ask away when you have a problem, preferably with the working out you’ve written down so far, so that others can lend a hand.

With 3/4 Reaction Pathways: Does anyone know if VCAA accepts H+ instead of H2SO4(l) or H3PO4(aq)???

Eg. Alkene + H2O → Alcohol {reagent: H3PO4 (aq)}
Eg. Alcohol + Carboxylic Acid → Ester {reagent: H2SO4 (l)}

Also - Can these two acids be used interchangeably? Or is H3PO4(aq) only used because it's aqueous - instead of a liquid.

Thanks!

    God
    You won't get away with H+ in either case

    It's incorrect to refer to the acids as "reagents" since they're catalysts. "Reagents" may have the connotation of the chemical species being consumed in the reaction eg acidified dichromate aka Jone's reagent in alcohol oxidation reactions.

    For alkene hydration VCAA actually accepts any inorganic strong acid except for HCl (because HCl adds onto the double bond). States aren't required for the catalyst for alkene hydration. However you should still specify H2O(g) with states

    VCAA only accepts concentrated H2SO4(l) for esterification, they don't accept anything else (which is overly pedantic since in uni chem we do all our esterification labs with a H3PO4 catalyst)

        Billzene
        Thanks so much Billzene! Legend 🙂

        So just to clarify - we could say H2SO4 for alkene hydration... ??? Also - could we ignore it's state for the oxidation of alcohols as well?
        Alcohol → Aldehydes → Carboxylic Acid (Reagents: Cr2O72-(aq) or MnO4-; Catalyst: H2SO4 (l))

        I think I'm just going to forget H3PO4 existed..... 😆

            God
            Technically you can state H2SO4 for alkene hydration, according to the 2020 examiner’s report. I was taught H3PO4, but since VCAA accepts any strong inorganic acid except HCl, you can assume H2SO4 is fair game

            For oxidation of alcohols, I think the state of the reagent is required. In VCAA exams, they don’t want you to write H2SO4 next to the oxidant (just H+). I usually write H+(aq)/MnO4-(aq) just cuz it’s easier to write (in uni chem you also learn that MnO4- is a better oxidant than dichromate, as well as being safer cuz Cr(VI) compounds are very carcinogenic).

                Hi everyone!
                Just a quick question:
                why is core charge always positive?

                Thank you!

                  PizzaMaster

                  Since core charge is given by number of protons in nucleus - number of non-valence e-s, and the number of non-valence e-s is always less than the number of protons in nucleus, core charge will always be positive

                    Can someone help me with this chemistry question?

                    There are a number of structural isomers for the molecular formula C4H10O. (Mass Spec Graph) Identify the fragment at 29 m/z.

                    The two possible answers are [C2H5]+ or [COH]+

                    My question is.... shouldn't the [COH] have a charge of +2? The molecule has lost two hydrogens...? not just 1 like in C2H5.....

                    Or does one electron drift off with the hydrogen, and the other one just happen to stay with the molecule?

                    Thanks!
                    -G

                      God For the purposes of VCE chem, you should assume that all fragments have a +1 charge.

                      "Or does one electron drift off with the hydrogen, and the other one just happen to stay with the molecule?"

                      This is called a radical, since they're uncharged, they won't be detected by the mass spec machine since it can only "see" charged fragments

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                          Struggling a bit with states for organic reaction pathways, always messing up gaseous and liquid states. Any tips?

                            robinsonada

                            H2SO4 should be (l) when it's catalysing an esterification because it's concentrated

                            Oxidising reagents are written as H+(aq)/Cr2O72- (aq) or H+(aq)/MnO4- (aq)

                            H2O will be (g) in alkene hydration since it's conducted at 300˚C

                            All reactants for esterification are (l) and not (aq) since water can hydrolyse the ester product back into the reactants

                              Hi everyone,
                              just quickly,
                              does a high melting point also mean that an element will have a high boiling point too?
                              thank you!

                                PizzaMaster
                                Most of the time - i'd say yes. High melting point means high intermolecular forces - which shouldn't disappear when it becomes a liquid. (Although, knowing chemistry...... )

                                  Can someone help with finding the splitting patterns in butanal?

                                  My question is.... for the hydrogen bonded to the C=O group, should it be a triplet or a singlet?

                                  If a triplet, shouldn't that mean the CH2 group (also bonded to the C=O) should be a quartet?

                                  Thanks! 🙂

                                    God
                                    The carbonyl hydrogen should be a triplet. The H environment on the alpha carbon has complex splitting so I don’t think VCAA will ask you that (it will be a quartet by the n+1 rule, but the reality is that the aldehyde H and the CH2 are in very different chemical environments that split the alpha carbon’s H environment by different amounts, so the observed pattern has a lot of overlapping peaks and isn’t a quartet. You’d call this a multiplet)

                                      Im currently doing U2 Aos1 but i don't get ions and charges at all

                                        When you are oxidising a primary alcohol, how do you prevent the reaction from going all the way to a carboxylic acid? It will first make an aldehyde, but how do I prevent the aldehyde from becoming oxidised?

                                        Alcohol ---> Aldehyde ----> Carboxylic acid MnO4-(aq) / H+(aq)