/0's Chem Questions

[NE2000]

an acid doesn't necessarily need to react with a base, it can react with carbonate, metal or oxide. However, keep in mind that carbonate and oxide are bases, as they accept protons, whereas with metal, it is a redox reaction between the metal atom and .

hmmm...

In unit two they tell us that an acid is not an acid unless a base is present. Because to be an acid, i.e. a proton donor, it requires a base to accept the protons. Likewise a reductant is only a reductant if an oxidant is present, which is especially relevant when you get to electrochemical series and the same thing can be a reductant/oxidant depending on the Eo value of the other thing present. Or maybe I'm misreading/misunderstanding something, could someone please clarify?

[Mao]

An acid, , donates a proton

this proton in turn acts as an oxidant, , and oxidises a metal.

It's the property that a proton is 'given away' that defines an acid, not that there's a base present.
Similarly, an oxidant is not present because there is a reductant, it is because it accepts electrons.

[NE2000]

An acid, , donates a proton

this proton in turn acts as an oxidant, , and oxidises a metal.

It's the property that a proton is 'given away' that defines an acid, not that there's a base present.
Similarly, an oxidant is not present because there is a reductant, it is because it accepts electrons.

OK I get it

[/0]

Thanks mao  

[/0]

When you're writing oxidation numbers, u know how for an ionic compound like

, you have to split it up into ions and and go from there...

Well, how are we meant to tell if something is ionic or covalent? Is there like... a vce list we have to know? I can recognise the basic ones but what about the complicated ones?

Because I just bumped into and I had no idea it was ionic. I have never seen nor heard of the ion!

[Mao]

as a rule of thumb, metals are usually always present as cations, with the rest being an anion molecule. Use your oxygen and hydrogen rules to work out oxidation numbers from there.

[/0]

as a rule of thumb, metals are usually always present as cations, with the rest being an anion molecule. Use your oxygen and hydrogen rules to work out oxidation numbers from there.

aiyah, chemistry and its many rules of thumb

thanks mao

[shinny]

Well, how are we meant to tell if something is ionic or covalent?

Unit 1/2 foundations strike again! Ionic bonding is a metal bonding with a non-metal. Covalent bonding is a non-metal bonding with another non-metal. Metallic bonding is a metal bonding with itself.

In your case, you can see that you have a chunk of stuff made up of a metal (sodium) and a non-metal (thiosulfate ion, well, at least that's what I recall it to be called o.O) so you should be able to recognise the existence of a ionic bond in there. The compound ion does make it a bit more complicated, but you should be able to see past that anyway.

[/0]

Can someone just confirm the oxidation numbers for ? Are they Cl: -1, O: 0?

[mark_alec]

Oxygen will be -2, Chlorine +1

[polky]

Can someone just confirm the oxidation numbers for ? Are they Cl: -1, O: 0?

Oxygen is always -2, other than particular exceptions (hydroxide or something).

[mark_alec]

http://goldbook.iupac.org/O04365.html as a reference.

[/0]

thanks =)

[/0]

The thermite process can be used to weld lengths of reailway track together. A mould placed over the ends of the two rails to be joined is filled with a charge of aluminium powder and iron(III) oxide. When the mixture is ignited, a redox reaction occurs to form molten iron, which join the rails together.

Write a half equation for the conversion of iron(III) oxide to form metallic iron.

I wrote

The answers have

I don't really get why they're allowed to split up the water molecule like that... and what's up with the state of in the second equation??? Would both answers be acceptable?

Also, the second part of the question:
Write the overall equation of the thermite process.

Please explain how you got it... thanks

[Mao]

I remember dealing with this question last year..

The 'mould' only contains iron oxide and aluminium, no H+. Hence your answer wouldn't be accepted [however, VCAA wouldn't put this question on an exam anyways]

In this case, Iron (III) is reduced to elemental iron, and elemental aluminium is oxidised to Al³⁺, i.e. the oxides changed owners, while energy was released.