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Similar to Polarity-of-Molecules-and-Its-Properties -.pptx (20)
Polarity-of-Molecules-and-Its-Properties -.pptx
- 1. Polarity of Molecules and Its Properties
- 2. OBJECTIVES After going through this module, you are expected to: 1.Define solubility, miscibility and polarity; 2.Identify the different types of intermolecular forces of attraction 3.Explain how polarity of molecules related to its properties
- 3. Polarity, Solubility, and Miscibility Polarity is a separation of electric charge leading to a molecule or its chemical groups having an electric dipole moment, with a negatively charged end and a positively charged end. Polar molecules must contain one or more polar bonds due to a difference in electronegativity between the bonded atoms. Solubility is defined as the ability of a solid substance to be dissolved in a given amount of solvent. Miscibility is the ability of the two liquids to combine or mix in all proportions, creating a homogenous mixture.
- 4. What chemistry concept did you used in answering the question above? If you answered polarity of molecules, then you are on the right track. Great job! Benzene and chloroform are both nonpolar compounds while water and vinegar are both polar compounds, thus they are miscible to each other. However, the rest is a combination of polar and nonpolar molecules and therefore will not mix and instead will form two layers even if shake nor carefully stirred. The general rule to remember about the solubility and miscibility of molecular compounds can be summarized in a phrase, “like dissolves like” or “like mixes with like”. This means that polar substances will only be dissolved or mixed with polar substances while nonpolar substances will be soluble or miscible with another nonpolar substance. Now I want you to try the exercises below in order to assess how much you have understood the solubility (and miscibility) rule of substances in relation to their polarity. Which of the following substances below will most likely mix with each other? a. water (H2O) and chloroform (CHCl) b. benzene (C6H6) and chloroform (CHCl3) c. water (H2O) and vinegar (CH3COOH) d. acetone (C3H6O) and toluene (C6H5CH3) e. carbon tetrachloride (CCl4) and water(H2O)
- 5. B. Bond Strength and Physical Properties of Covalent Compound From the previous module, you learned the intramolecular forces of attraction, the attractive force that binds atoms together. In this module, you will learn another type of attractive force, the intermolecular forces of attraction (IMFA) which exists between molecules. 1.There are several types of IMFA and below they are arranged from STRONGEST to WEAKEST. Ion-dipole →H-bonding→dipole- dipole→dipole-induced dipole→London forces of attraction. 2. The strength of IMFA greatly affects the physical properties of substances such as boiling point, melting point, vapor pressure, surface tension, etc.
- 6. Table 1: shows the comparison of the various types of IMFA while table 2 shows the physical properties of polar and nonpolar molecules as affected by the type of IMFA present.
- 7. Table 2. General Properties of polar and nonpolar molecule
- 8. Let us define the physical properties of substance: A. Boiling point: temperature at which the vapor pressure and atmospheric pressure of a liquid substance are equal. B. Melting point: temperature at which solid becomes liquid. At this point, the solid and liquid phases exist in equilibrium. C. Surface tension: energy needed to increase the surface area by a unit amount; D. Viscosity: the resistance of the liquid to flow. E. Vapor Pressure: pressure exerted by a substance in its gaseous state. F. Volatility: measures the rate at which a substance vaporizes(changes from liquid to gas) In the simplest sense, boiling point, melting point, viscosity and surface tension increase as the strength of intermolecular forces increases. On the other hand, vapor pressure and volatility decrease with increasing strength of IMFA. London dispersion forces increase as the molecular mass of a substance increases. Unlike in H-bonding, as the molar mass increases, the boiling point, melting point, viscosity and surface tension decrease.