Polar vs nonpolar lab
Background
Some substances dissolve well in water while others do not. The answer lies
in the polarity of the molecules in both the solvent and the solute. A
molecule is polar if its center of positive charge is in a different location that
its center of the electronegative charge. Water is the best example of this.
The electronegativity of hydrogen is 2.1 while oxygen has 3.5. The charge
separation in water is responsible for its unique properties. Some solvents
are nonpolar and will not dissolve in water. A nonpolar solvent does not
have this large electronegativity difference. These are considerations taken
into account in the drycleaners business. They need to have solvents on hand
that will dissolve different substances out of clothing.
Remember that more is not better in this lab-you will have a hard time
telling if things are dissolving
Prelab
1.Make a sketch showing the attractions of water molecules to each other
2.Make separate sketches indicating the attractive forces between water
molecules and anion and cations-such as water dissolving NaCl:
Materials
Copper chloride, sucrose, naphthalene, ethanol, vegetable oil, ammonium
nitrate, water, hexane, goggles
1cm water + 8-10drops of solute/or 2-3 small grains of solute
1cm hexane + 9-10 drops of solute/2-3 small grains of solute
Data
Solute
behavior in water H2O behavior in hexane
Copper II chloride
(CuCl2)
Sucrose
(C12H22O11)
Naphthalene
(C10H8)
Ethanol
(CH3CH2OH)
Vegetable oil
CH3(CH2)16COOH
Ammonium nitrate
NH4NO3
CH2CHCHCHCHCH2
Analysis
1.Divide the solutes into two groups(nonpolar and polar) and list:
2.What are some similarities between solutes that dissolve in water ONLYyou may include such aspects as electronegativity?
3.What are some similarities between solutes that dissolve in hexane ONLYyou may include such aspects as electronegativity?
4.For the solutes that had some affinity for both water and hexane, describe
the structural reasoning as to why they behaved this way.