Polarity
Purpose:
This lab will attempt to show the nature of the attractive forces between molecules and how that affects the solution process and the selectivity of solvents. The general rule of solubility is
Like dissloves LikeNonpolar liquids dissolve in each other because of weak van der Waals forces. These exist in all matter and are called induced dipolar forces. Nonpolar substances do dissolve in polar liquids to a greater or lesser extent because of van der Waals forces. Polar liquids have varying degrees of polarity and dissolve in each other because of dipole-dipole interactions. These forces play an important role in determining its melting point, boiling point and vapor pressure. Various alcohols act like water in relation to hydrogen bonding. One measure of polarity is the dielectric constant which follows for the materials indicated. Acetone is 1.0; toluene is 2.4; ethanol is 24.3; ethylene glycol is 37; glycerol is 42.5 and water is 80.37. If you are trying to get rid of a stubborn stain on clothing and soap and water does not work try nail polish remover (not on some synthetics) on a piece of the fabric where damage will not show.
Work under the hood with acetone and/or toluene with the fan on. Use only glass with these substances.
Procedure 1:Put one (1) milliliter of the above liquids into different testubes. Add a small iodine crystal to each testube using forceps. Do not touch iodine with your fingers. Stopper each testube and shake vigorously. The color of the resulting solution indicates the solubility and polarity of iodine in solution. Compare the colors to the dielectric constants and record under data.
Procedure 2:Use four (4) clean and dry testubes and take them to the hood. Into each testube place one milliliter of acetone or a designated chemical. Then to the first testube add one ml. of water. The second testube add one ml. of ethanol. The third testube add one ml. of ethylene glycol and the fourth testube add one ml. of glycerol. Stopper and shake each tube. Watch for separation of liquids upon standing. Separation indicates immiscibility.
Now add one ml. of ethanol to each testube that you just checked for separation. Stopper and shake them. Measure the height of the layers formed and tell what substances dissolved in the ethanol. On the basis of the results obtained, list the liquids used in order of increasing polarity.
Conclusion
- Based upon what iodine dissolves into is iodine highly polar, slightly polar or nonpolar.
- What is the accepted dielectric constant for iodine. Does this match what iodine dissolved best into from question 1?
- Why does iodine dissolve in ethanol, but not so well in glycerol even though both liquids are alcohols?
- For the alcohols used, what apparent effect does increasing the number of (OH) groups in a compound have on it's polarity?
- Tell what experimental evidence supports the idea of "Like dissolves Like".
- Methanol and ethanol are cheap materials that are used for "dry gas". Why do they prevent gas line freeze-ups?
- What is in tincture of iodine (or Betadine) that is used on cuts.
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Nonpolar liquids dissolve in each other because of weak van der Waals forces. These exist in all matter and are called induced dipolar forces. Nonpolar substances do dissolve in polar liquids to a greater or lesser extent because of van der Waals forces. Polar liquids have varying degrees of polarity and dissolve in each other because of dipole-dipole interactions. These forces play an important role in determining its melting point, boiling point and vapor pressure. Various alcohols act like water in relation to hydrogen bonding. One measure of polarity is the dielectric constant which follows for the materials indicated. Acetone is 1.0; toluene is 2.4; ethanol is 24.3; ethylene glycol is 37; glycerol is 42.5 and water is 80.37. If you are trying to get rid of a stubborn stain on clothing and soap and water does not work try nail polish remover (not on some synthetics) on a piece of the fabric where damage will not show.
Put one (1) milliliter of the above liquids into different testubes. Add a small iodine crystal to each testube using forceps. Do not touch iodine with your fingers. Stopper each testube and shake vigorously. The color of the resulting solution indicates the solubility and polarity of iodine in solution. Compare the colors to the dielectric constants and record under data.
Procedure 2:Use four (4) clean and dry testubes and take them to the hood. Into each testube place one milliliter of acetone or a designated chemical. Then to the first testube add one ml. of water. The second testube add one ml. of ethanol. The third testube add one ml. of ethylene glycol and the fourth testube add one ml. of glycerol. Stopper and shake each tube. Watch for separation of liquids upon standing. Separation indicates immiscibility.
Now add one ml. of ethanol to each testube that you just checked for separation. Stopper and shake them. Measure the height of the layers formed and tell what substances dissolved in the ethanol. On the basis of the results obtained, list the liquids used in order of increasing polarity.
Conclusion
- Based upon what iodine dissolves into is iodine highly polar, slightly polar or nonpolar.
- What is the accepted dielectric constant for iodine. Does this match what iodine dissolved best into from question 1?
- Why does iodine dissolve in ethanol, but not so well in glycerol even though both liquids are alcohols?
- For the alcohols used, what apparent effect does increasing the number of (OH) groups in a compound have on it's polarity?
- Tell what experimental evidence supports the idea of "Like dissolves Like".
- Methanol and ethanol are cheap materials that are used for "dry gas". Why do they prevent gas line freeze-ups?
- What is in tincture of iodine (or Betadine) that is used on cuts.
Back to top
Use four (4) clean and dry testubes and take them to the hood. Into each testube place one milliliter of acetone or a designated chemical. Then to the first testube add one ml. of water. The second testube add one ml. of ethanol. The third testube add one ml. of ethylene glycol and the fourth testube add one ml. of glycerol. Stopper and shake each tube. Watch for separation of liquids upon standing. Separation indicates immiscibility.
Now add one ml. of ethanol to each testube that you just checked for separation. Stopper and shake them. Measure the height of the layers formed and tell what substances dissolved in the ethanol. On the basis of the results obtained, list the liquids used in order of increasing polarity.
Conclusion
- Based upon what iodine dissolves into is iodine highly polar, slightly polar or nonpolar.
- What is the accepted dielectric constant for iodine. Does this match what iodine dissolved best into from question 1?
- Why does iodine dissolve in ethanol, but not so well in glycerol even though both liquids are alcohols?
- For the alcohols used, what apparent effect does increasing the number of (OH) groups in a compound have on it's polarity?
- Tell what experimental evidence supports the idea of "Like dissolves Like".
- Methanol and ethanol are cheap materials that are used for "dry gas". Why do they prevent gas line freeze-ups?
- What is in tincture of iodine (or Betadine) that is used on cuts.
Back to top
- Based upon what iodine dissolves into is iodine highly polar, slightly polar or nonpolar.
- What is the accepted dielectric constant for iodine. Does this match what iodine dissolved best into from question 1?
- Why does iodine dissolve in ethanol, but not so well in glycerol even though both liquids are alcohols?
- For the alcohols used, what apparent effect does increasing the number of (OH) groups in a compound have on it's polarity?
- Tell what experimental evidence supports the idea of "Like dissolves Like".
- Methanol and ethanol are cheap materials that are used for "dry gas". Why do they prevent gas line freeze-ups?
- What is in tincture of iodine (or Betadine) that is used on cuts.