April 1, 2015

Homework Help: science(chem)

Posted by ~christina~ on Sunday, September 2, 2007 at 9:11pm.

A few questions.

1. What is the difference btwn crystalization and precipitation?

2. What will happen if you choose a solvent whose boiling point is higher than the melting point of the compound to be crystalized?

3. Generally describe how to predict solubility.

1. just checking my thinking on this. Crystalization is the actual process of forming crystals while precipitation is actually getting a solid out of solution right?

2. No clue ..

3. To predict solubility:(my thinking)
a) determine if the molecule to be dissolved is polar or nonpolar since like dissolves like.

b)hydrocarbons = nonpolar
1. the more carbons on a compound the more hydrocarbonlike it is.

c)If it has a electronegative atom in the compound such as N and O then it is polar.
1. If the atom is a halogen thus having high electronegativity then it is polar but not alot since the halogen doesn't have a great effect on the organic compound.

2. If the molecule has a few carbons compared with alot of carbons and also has a electronegative atom in the compound then the one with fewer is more soluble in water b/c water is polar and the fewer carbons it has would make it more polar and having more carbons would make it more hydrocarbon like. (less polar)

d) Compounds that belong to the same "family" are soluble with each other but only if their size is similar. If there is a great size difference then that doesn't work.

e)dipole dipole forces of attraction btwn the hydrogens of one molecule and the electronegative atom in another molecule. (F,O,N)

Is this correct?
I'm not sure how to make my explanation for #3 in general terms (shorter abreviated form)

Thanks =)

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