/0's Chem Questions

[shinny]

It depends what type of acids and bases you're mixing. If it's a strong acid with strong base, then your assumption is correct. However, if one or both are weak (shouldn't be titrating two weak solutions to begin with though), then one of them isn't fully ionised in terms of or particles, and it won't be at 7. I'll elaborate more if you want but you seem to understand stuff pretty well anyhow and hopefully that's enough to point you in the right direction.

[/0]

It depends what type of acids and bases you're mixing. If it's a strong acid with strong base, then your assumption is correct. However, if one or both are weak (shouldn't be titrating two weak solutions to begin with though), then one of them isn't fully ionised in terms of or particles, and it won't be at 7. I'll elaborate more if you want but you seem to understand stuff pretty well anyhow and hopefully that's enough to point you in the right direction.

Yep, sure is! Thanks again

[/0]

The ionic equation for



is



Why do you dissociate but not ? 

[shinny]

HCl is an ionic compound, made of the H+ ion and the Cl- ion. On the other hand, NH3 is a covalent molecule and doesn't actually dissociate in water like ions do since covalent molecules are joined by covalent bonds, as opposed to ions which just bond to the water molecules in most cases.

EDIT: I blame drugs.

[/0]

HCl is ionic? Ahah I always thought it was covalent! I thought anything with H is a covalent molecule. Thanks shinny

[Mao]

HCl is covalent, but H comes off very easy because Cl is very electronegative.

NH3 on the other hand, is basic, it would rather accept H+ than give away.

[/0]

If something is highly electronegative doesn't that mean it will strongly attract electrons i.e. the bond in HCl will be strong?

[shinny]

Ah whoops sorry, not thinking right x_x Summer holidays is killing my head.

[Mao]

If something is highly electronegative doesn't that mean it will strongly attract electrons i.e. the bond in HCl will be strong?

When you hug too hard, you suffocate the girl. Same principle

[/0]

If something is highly electronegative doesn't that mean it will strongly attract electrons i.e. the bond in HCl will be strong?

When you hug too hard, you suffocate the girl. Same principle

okey dokey...

 

[Mao]

If something is highly electronegative doesn't that mean it will strongly attract electrons i.e. the bond in HCl will be strong?

When you hug too hard, you suffocate the girl. Same principle

okey dokey...

 

okay, I meant, Cl wants the electron so badly that, it rips it off the hydrogen.

[kurrymuncher]

lo this reminds me of year 8 science class when had to watch a video where hydrogen and chlorine atoms are at a club, trying to pick up other atoms and bond.

[NE2000]

If something is highly electronegative doesn't that mean it will strongly attract electrons i.e. the bond in HCl will be strong?

When you hug too hard, you suffocate the girl. Same principle

okey dokey...

 

okay, I meant, Cl wants the electron so badly that, it rips it off the hydrogen.

Yeah it's just like in unit two, an acid is where the hydrogen is bonded to a highly electronegative atom so much so that the electronegative atom almost has exclusive control over the electron and the hydrogen can be ripped off (by a base) without taking its electron with it. i.e. it's just a proton being removed from the acid.

so I would guess the relavence to the ionic equation is that HCl compltely ionizes in water and hence you say there's an H+ and Cl- (the conjugate base) while NH3 is going to remain in its molecular form until it becomes that ammonium ion (the reaction).

[/0]

Ok thanks I think I get it now... but if an acid reacts with a metal, metal oxide, metal carbonate, or metal hydrogen carbonate, they ionise even though they are bases. Or... wait, is it because those reactions are not defined as bronsted-lowry reactions, so the metal thingies don't even act as bases?

Also, when sketching pH curves, do we have to put the coordinates (or at least the y-coordinate) of the equivalence point, or can it be (like the rest of the graph) a rough estimate? I'm a bit fuzzy with the shape of weak-acid-weak-base curves, is it important to know?

And also (lol) in a reaction between NaOH and a strong acid, the solutions say the best indicator would be Methyl Orange. However, Methyl Orange changes colour in the pH range of 3.2-4.4. Since the neutralisation reaction will have an equivalence point very near pH=7, shouldn't bromothymol blue be used, since it changes colour over pH 6.0-7.6?

[Mao]

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 .

as for pH curves, don't worry about coordinates of equivalence point. The only thing definite about equivalence point is that , which doesn't take into account the conjugate acid/base in the solution, hence at that point, pH is not necessarily 7.

and as for strong vs strong, the choice of indicator doesn't really matter that much, as the transition from acidic to basic [or vice versa] is extremely rapid. Look in your textbook for the titration curve and you'll see that 3.2-4.4 doesn't really affect it that much. Remember that in chemistry, choice of chemicals aren't only decided by what works best, but also abundance/price