/0's Chem Questions

[/0]

What is the word for when you heat a solid until it 'evaporates'? I know the word isn't evaporate but I can't remember what the technical word is

[TrueTears]

Sublime?

[Mao]

What is the word for when you heat a solid until it 'evaporates'? I know the word isn't evaporate but I can't remember what the technical word is

melt?

A solid can evaporate, e.g. dry ice (CO2 solid) evaporates to CO2 gas

[/0]

I mean like, say you have AgCl precipitate and you heat it too hot in an oven, what's that called?

[chem-nerd]

drying? 

it would take a fair bit of heat to make AgCl change its state

[hyperblade01]

Sublimation is when a solid changes into a gas without going through the liquid stage, forgot what you call it when its the other way round....

[/0]

Oops I don't think I correctly described what I was looking for soz... anyway I think I was looking for decomposition

[/0]

Also, in NEAP 2008 they say that 'trimyristate' (made of glycerol and myristic acid) "reacts with methanol in the presence of excess sodium hydroxide to form glycerol and large organic molecules that are the main components of biodiesel."

The equation is:



I would think the blank is myristic acid but it turns out it's an ester? How can this be?

[d0minicz]

wouldnt it hydolyse into the 3 fatty acids + gycerol; then you combine the fatty acids and methanol to give biodiesel + water :S

[ryley]

If you look at that massive molecule on the left of the equation, that is the oil trimyristate. So I think what they've done is combine the "oil + water --> glycerol + fatty acid + methanol --> ester + glycerol (leftover from previous step) + water" process by canceling out the water molecules and combining the two steps.

EDIT: Damn it, beat again  :idiot2:

[/0]

Ah k thanks

[Mao]

This is called 'transesterification', 'trans' because one of the R group is changed.

The reaction is triglyceride + 3 methanol --> glycerol + 3 methyl-ester

in this case, the fatty acid changes from being an ester with the glycerol to being an ester with methanol. The catalyst is KOH or NaOH

[/0]

thanks mao

Also consider the two molecules:


What is the number of peaks in the middle hydrogens?

Do they differ? thnx

[TrueTears]

thanks mao

Also consider the two molecules:


What is the number of peaks in the middle hydrogens?

Do they differ? thnx

Yes they do.

[/0]

Is this right:
(4+1)=5?
(2+1)(2+1) = 9?
thhx tt