General Chemistry 2 Summary of Learnings PDF

**KINETIC MOLECULAR THEORY** - It is a theory that explains the states of matter and is based on the idea that matter is composed of tiny particles that are always in motion. **POSTULATES OF KINETIC MOLECULAR THEORY** 1. Matter is made of particles that are constantly in motion. The...

**KINETIC MOLECULAR THEORY** - It is a theory that explains the states of matter and is based on the idea that matter is composed of tiny particles that are always in motion. **POSTULATES OF KINETIC MOLECULAR THEORY** 1. Matter is made of particles that are constantly in motion. The energy in motion is called **kinetic energy.** 2. The amount of kinetic energy in a substance is related to its temperature. **The relationship between kinetic energy and temperature is directly proportional.** 3. There is space between particles. **The amount of space in between particles is related to the substance's state of matter.** 4. Phase changes happen when the temperature of the substance changes sufficiently. 5. There are attractive forces in between particles called **intermolecular forces**. The strength of these forces increase as particles get closer to each other. ***STATE OF MATTER*** STATE ARRANGEMENT OF PARTICLES MOTION OF MOLECULES SHAPE VOLUME COMPRESSIBILITY DENSITY -------- --------------------------------------------------------------------- ---------------------------------- ------------ ------------ ---------------------- ------------------------------------ SOLID Particles were compacted having no distance between them. Vibration Definite Definite Cannot be compressed More dense LIQUID Particles were "slightly" far away from each other. Particles slide past each other. Indefinite Definite Cannot be compressed Less dense than solids GAS Particles were spread out and has a great distance from each other. Indefinite Indefinite Less dense than solids and liquids NOTES: - **Solid has the greates force of attraction between particles. Next to solids are liquids. In gases, there is a little attraction between its particles.** **INTERMOLECULAR FORCES** ***MOLECULES*** - Formed when two or more atoms join together chemically. - **Diatomic Molecules** - Made of two atoms of the same element. - Hydrogen, Nitrogen, Oxygen, Fluorine, Chlorine, Bromine, Iodine, Astatine ***INTERMOLECULAR FORCE*** - Attractive forces **between molecules, between ions, or between ions and molecules.** - What is the difference between INTERmolecular forces and INTRAmolecular forces? - INTRAMOLECULAR FORCES hold atoms together in a molecule. - INTERMOLECUAR FORCES are attractive forces between molecules. *DIPOLE-DIPOLE FORCES* - Attractive forces between **polar molecules.** - Polar molecules have permanent dipoles of neighnoring molecules. - Polar molecules have a high melting and boiling points than nonpolar molecules of similar molar mass. *HYDROGEN BONDING* - It is a special case of dipole-dipole forces and only exists between **hydrogen atoms bonded to F, N, or O and F, N, and O atoms bonded to hydrogen atoms.** - It is especially strong in biological systems such as DNA. *ION-DIPOLE FORCES* - Attractive forces between an **ion and a polar molecule.** - A negative ion attracts the positive dipole of another molecule. - A positive ion attracts the negative dipole of another molecule. *ION-ION FORCE (IONIC BOND)* - The strongest force - Ion-ion forces increase as the size of ion decreases and as the magniture of the charge increases. - Anions are larger than the atoms they are derived from and cations are smaller than the atoms they are derived from. *LONDON DISPERSION FORCES/VAN DER WAALS FORCES* - Interactions involving **induced dipoles.** - Non-polar molecules have no permanent dipole moment, but transient dipoles exist due to the random motion of the electrons about the positive charge center. - These are weak forces. **LEWIS DOT STRUCTURE** - Created by Gilbert Lewis in 1916 - It shows structural formula for compounds - Arrangement of atoms and bonds within a compound. - It uses **valence electrons (or the outermost electrons)** - One dot = one valence electron - One dash = a covalent bond = two electrons ***LEWIS STRUCTURE*** - It shows how valence electrons are arranged among atoms in a molecule. - Reflect the idea that stability of a compound relates to the octet rule. - Shared electons pairs are covalent bonds and can be represented by two dots or by a single line. ***HONC RULE*** - **H**ydrogen and Halogens form one covalent bond. - **O**xygen and Sulfur form two covalent bonds. - One double bond, or two single bonds. - **N**itrogen and Phosphorus form three covalent bonds. - One triple bond, or three single bonds, or one double bond and one single bond. - **C**arbon and Silicon - Two double bonds, or four single bonds, or one triple and one single, or one double and two singles. ***LEWIS DOT STRUCTURES -- COMPOUNDS*** - Hydrogen only needs two valence electrons to be stable. - Boron is the only exception, it only needs 6 valence electrons to be stable. - Atoms in the third row and below can disobey the octet rule at various times. ***CARBON-BASED MOLECULES*** - With multiple carbon compounds, connect carbons together. - Examples: - Ethane - Ethene - Ethyne - Ethanol - Formaldehyde - Benzene - Acetic Acid **MOLECULAR GEOMETRY** - Based on **Valence Shell Electron Pair Repulsion (VSEPR) Theory** - Electron pairs around central atom, arrange themselves so they can be as far apart as possible from each other. - You will be responsible for five molecular shapes - Compounds take a three-dimensional shape based on: - Number of atoms attached - Number of unbonded electrons present - ***LINEAR*** - Carbon is central atom - Surrounded by two oxygen atoms - No unbonded electrons on carbon - Look for AX2 geometry - Central atom is group 14. - ***BENT*** - Oxygen is central atom. - Central atom is typically group 16. - Surrounded by two atoms (H or Halogens) - Two unbonded electron pairs on oxygen, push Hydrogens out of the plane. - ***TRIGONAL PYRAMIDAL*** - Nitrogen surrounded by three hydrogen atoms (or halogens) - One pair of unbonded electrons, push Hydrogens out of plane. - ***TRIGONAL PLANAR*** - Boron is central atom surrounded by three fluorine atoms (or H or other Halogen). - No unbonded electrons on boron, fluorine atoms stay within a single plane. - ***TETRAHEDRAL*** - AX4 formula - Carbon (or silicon) surrounded by four hydrogen (or halogens). **POLARITY** - ***Bond Polarity*** - Difference in electronegativity between two atoms in a chemical bond. **BOND/POLARITY** **DIFFERENCE IN ELECTRONEGATIVITIES** ------------------- --------------------------------------- **NON-POLAR** **Less than or equal to 0.4** **POLAR** **0.5 -- 1.6** **IONIC** **Greater than 0.6** **MOLECULAR POLARITIES** - Polar molecules occur when electrons are not distributed equally. - Look for symmetry within molecule. - If symmetrical, then it is non-polar. - If asymmetrical, then it is polar. - **POLAR SHAPES:** - Trigonal pyramidal - Bent - Nonpolar molecules occur when electrons are distributed equally. - **NONPOLAR SHAPES:** - Linear - Trigonal Planar - Tetrahedral **PROPERTIES OF LIQUID** ***SURFACE TENSION*** - The property of the surface of a liquid that allows it to resist an external force, due to the cohesive nature of its molecules. - TENSION - The stae of being stretched tight. ***VISCOSITY*** - Resistance of a fluid (liquid or gas) to a change in shape, or movement of neighboring portions relative to one another. ***VAPOR PRESSURE*** - A measure of the tendency of a material to change into the gaseous or vapour state. ***BOILING POINT*** - Temperature at which the vapour pressure is equal to the standard sea-levl atmospheric pressure. ***MOLAR HEAT VAPORIZATION*** - Amount of heat required to vaporize 1 mole of liquid. **PROPERTIES OF WATER** **WATER** - Composed of two hydrogen atoms and one oxygen atom. - They are attracted to each other due to their electrostatic attraction. - Hydrogen atom is positively charged, while Oxygen is negatively charged. - The hydrogen of one water molecule will bond to the oxygen atom of another molecule. PROPERTIES OF WATER 1. Boiling and Freezing Point - Since water has a strong intermolecular forces of attraction caused by the formation of the H-bond, its boiling point is high. - At higher elevations (lower atmospheric pressure), water's boiling temperature decreases. This is why it takes longer to boil an egg at higher altitudes. - If a substance is dissolved in water, the freezing point is lowered. Energy is lost when water freezes. - A great deal of heat is released into the environment when liquid water changes to ice. 2. Surface Tension - Hydrogen bond formation among water molecules causes water to have high surface tension. Is is called capilliarity. - Surface tension is essential for the transfer of energy from wind to water to create waves. 3. Cohesion - Water molecules stick to each other due to the hydrogen bonds among the molecules. - The water molecules at the surface crowd together, producing a strong layer as they are pulled downward by the attraction of the water molecules beneath them. 4. Adhesion - Water molecules stick to other substances. - This is how water makes things wet. It also clings to living things. 5. Thermal Properties - Water absorbs or releases more heat than many substances for each degree of temperature increase or decrease. - Because of this, it is widely used for cooling and for transferring heat in thermal and chemical processes. 6. Heat of Vaporization - A large amount of heat is needed to vaporize a given amount of water. This cuses a significant drop in temperature during evaporation. - When molecules of water absorb heat energy, they move fast in the water. If the speed of the movement some molecules becomes so fast, it allows them to overcom intermolecular attraction, making them to detach from the multi-molecular water, form bubbles, and leave the water surface in the gas state. 7. pH Level - A neutral solution contains an equal number of Hydroxide ions and Hydrogen ions. It is acidic if there's a greater concentration of Hydrogen ions. It is alkaline or basic if there's a greater concentration of Hydroxide ions. CONCENTRATION OF SOLUTION MOLARITY - Number of moles of solute dissolved in one liter of solution. - Formula: - Molarity (M) = [\$\\frac{\\text{moles\\ of\\ solute}}{\\text{liters\\ of\\ solution}}\$]{.math.inline} MOLALITY - Concentration unit based on the number of moles of solute per kilogram of solvent - Formula: - Molality (m) = [\$\\frac{\\text{moles\\ of\\ solute}}{\\text{kg\\ of\\ solvent}}\$]{.math.inline} PERCENT BY MASS - Percent by mass = [\$\\frac{\\text{mass\\ of\\ solute}}{\\text{mass\\ of\\ solution}}\$]{.math.inline} - Represented by grams PERCENT BY VOLUME - Percent by volume = [\$\\frac{\\text{volume\\ of\\ solute}}{\\text{volume\\ of\\ solution}}\$]{.math.inline} - Represented by milliliters **YIELD** - A measure of the quantity of moles of a product formed in relation to the reactant consumed, obtained in a chemical reaction, usually expressed as a percentage. **THEORETICAL YIELD** - Expected amount of a product after the reaction **ACTUAL YIELD** - The actual yield is the amount of product that is actually formed when the reaction is carried out in the laboratory. **PERCENTAGE YIELD** - The percent ratio of actual yield to the theoretical yield **HOW TO GET THE PERCENTAGE YIELD?** - It is calculated to be the experimental yield divided by theoretical yield multiplied by 100% - [\$\\frac{\\text{Actual\\ yield}}{\\text{Theoretical\\ yield}}\*100\\%\$]{.math.inline} - BONUS: - Theoretical Yield: [\$\\frac{\\text{Actual\\ yield}}{\\text{Percentage\\ yield}}\*100\\%\$]{.math.inline} - Actual Yield: [\$\\frac{\\text{Percentage\\ yield}}{100}\*Theoretical\\ Yield\$]{.math.inline} **LIMITING REACTANT** - Reactant that gets consumed first in a chemical reaction and therefore limits how much product can be formed. **HOW TO FIND THE LIMITING REACTANT?** EXAMPLE: H~2~ + O~2~ H~2~O (4 g of Hydrogen, and 10 g of Oxygen) **First Step: Balance first the equation** - 2H~2~ + O~2~ H~2~O **Second Step: Divide the atomic mass to the given grams** - For Hydrogen: [\$\\frac{4\\ g}{1.01\\ g/mol} = 3.96\$]{.math.inline} mol - For Oxygen: [\$\\frac{10\\ g}{16\\ g/mol} = 0.63\$]{.math.inline} mol **Third Step: Divide the coefficient of each reactant to its quotient after step 2** - For Hydrogen: [\$\\frac{3.96\\ mol}{2} = 1.98\\ mol\$]{.math.inline} - For Oxygen: [\$\\frac{0.63\\ mol}{1} = 0.63\\ mol\$]{.math.inline} **ANSWER: The limiting reactant is Oxygen (smallest quotient).** **GOOD LUCK!**