You were instructed to rinse the filter pipettes with methanol and with hexane. obviously the reason for this is to remove any contaminants that may be present on the glass or cotton. using what you learned about the physical properties of organic compounds in 40a, why were the solvents methanol and hexane chosen?

See explanation below.

Explanation:

The compounds can be polar or nonpolar. The dipolar moment for a nonpolar molecule must be 0. Because of this difference, the compounds have different properties, and the solubility is one of the most affected, polar molecules dissolve polar molecules, and nonpolar molecules dissolve nonpolar molecules.

Hexane is a hydrocarbon, and all the hydrocarbons are nonpolar, so it is a good solvent for nonpolar compounds. Methanol is alcohol, which has the hydroxyl group (OH) so it's a polar molecule and a good solvent for polar compounds.

That's why the both are chosen: hexane removes the nonpolar contaminants, and methanol the polar contaminants.

  the   balanced   equation   for   reaction of   ca metal   with   o2 to   produce   cao   is as below

2 ca+ o2→ 2 cao2

  explanation

the reaction is   balanced     since the   number of atoms   in reactant side is   equal to   number of atoms   in   product side.   for   example   they   are 2   atom of   ca in   reactant   side   and   2   atoms of ca   in   the product side.

  the   process   is a   meet the   requirement   of   redox   reaction because :     calcium   is   oxidized   from   oxidation state 0   to 2+   while   oxygen   is reduced from   oxidation   state   0   to 2-

i do not get it   at all