Question

Compounds: Name & Condensed structure Polar bonds? Polar or Non- polar Molecule? Dipole moment (D) (YES or NO) Water: Yes Polar Molecule 1.8546 d H2O Hexane: No 0.08 d Non-Polar Molecule CH3CH2)4CH3 Ethanol: Yes Polar Molecule CH3CH2OH Acetone: CH3C(EOẠCH Classify the substances from the least polar to the most polar: Least Polar Most Polar What are the dominant intermolecular forces occurring between molecules of each of the substances? Water: Ethanol: Acetone:

Answer 1

The strength of inter-molecular force is as follows: A. Water polar, dipole moment- 1.8546 d B. Hexane non-polar 0 d C. Ethanol polar 1.69 d D. Acetone polar 2.91d Intermolecular forces are the forces that act between molecules to other molecule as attraction. These are mainly three types: Hydrogen bonding > dipole dipole interaction > dispersion or London force 1. Dipole-dipole interaction 2. Hydrogen bond 3. London force. Least polar to most polar Hexane < ethanol <water < acetone Dipole-dipole interaction: This type of interaction forces is found between polar molecules. The strength of this force is increasing with increasing polarity of molecules. The boiling and melting point of the compounds depends on the strength of the functional groups, so first we will see at the functional groups to determine the strength of the intermolecular forces. The stronger the forces, the higher the boiling and melting point. Acetone is a polar molecule Intermolecular force The presence intermolecular force in alcohol and water is as follows: CH.CH,OH Ethanol an alcohol 1. Dipole-dipole interaction 2. Hydrogen bond 3. London force. Hydrogen bond: Generally hydrogen bond is found in those molecules which have covalently hydrogen atom bonded with high electronegative atoms like oxygen, nitrogen and fluorine. In the covalent molecules the sharing electron moves towards these high electronegative atoms as the result they have partially negative charge and hydrogen atom contains partially positive charge. When these opposite charge come together they form hydrogen bond. Hydrogen bond is a type of intermolecular force which is denoted by dotted line. Alcohol: The intermolecular force in alkane (hexane ) is only London force The presence intermolecular force in acetone is as follows: Alcohol contains 0-H bonds; where the electro negativity difference between 0-1 is 1.4 hence this bond is polar. Ether: 1. Dipole-dipole interaction 2. London force. The presence intermolecular force in alcohol is as follows: Increasing strength of intermolecular force: London force: London force is an intermolecular force which occurs between an atoms or molecules which are polar or non-polar and another atom or molecule which are polar or non-polar. Hence it occurs between all molecules or atoms. The London dispersion force is a temporary attractive force which cause due to temporary dipoles of electrons in two adjacent atoms. This is also known as induced dipole-induced dipole attraction. It is a weakest Intermolecular force. 1. Dipole-dipole interaction 2. Hydrogen bond 3. London force. Hexane <acetone <alcohol <water Alkane: In alkane; only c-hbonds present which have the electro negativity difference between c-h is 0.35 hence this bond is non-polar. The intermolecular force in alkane (hexane ) is only London force because they are not polar and not contains covalently hydrogen atom bonded with high electronegative atoms like oxygen, nitrogen and fluoring