Lecture Notes - Intro to Chem

08-13-19 CHEMISTRY - The study of properties, structure, composition and reactions of matter. MATTER - Anything that has mass or occupies space. (Table, Me, O2, Earth, Protons, Virus, Photons, Light) OBSERVATION OF MATTER: Microscopic - molecular biologists, biologists, medical professionals Macroscopic - Zoologists, astrophysicists, Particulate Level - Chemists, nuclear physicists DECREASE OF FREEDOM of particles (matter) - the Big Bang created space, time and matter. How could nothing create everything? This does not mean however, all matter as it came from the same place, it all behaves the same. Matter has different degrees of freedom: TRANSLATIONAL FREEDOM - The ability of the particles or matter to move around it’s space, from one place to another. ROTATIONAL FREEDOM - The ability of particles or matter to rotate around a point in space. VIBRATIONAL FREEDOM - The ability of particles or matter to wiggle in time rather than space. A wave, the ability of particles to oscillate in time AND space. States of Matter: Liquid - definite volume, indefinite shape of container, moderate density, vibrational, rotational, non-compressible Gas - indefinite shape and volume, low density, non-viscous, compressible vibrational, rotational, translational Solid - high density, fixed volume and shape, non-compressible, vibrational. 08-15-19 Matter (Types: Gas, Liquid, Solid) Potential energy: A -> B + Heat Exothermic (exo = out), energy is moving out of the system A + Heat -> B Endothermic (endo = in), energy, heat is absorbed in the system A+B -> C+D Reactants Products MATTER Mixture: Is composed of two or more Different types of chemicals/molecules. (Saltwater, Air, Milk) Pure substance: Is composed of one type of Chemical/molecule. (H2O, Glucose, Fe) PURE SUBSTANCE Compound: Is composed of two or more Types of atoms. It can be chemically separated To its elements. (C6H12O6, H2O, C2H5OH) Element: Is composed of one type of atom. It cannot be broken down further down Into anything else. (Fe, Na, Mg) 7 Diatomic elements: H2, N2, O2, Cl2, F2, Br2, I2 MIXTURE Homogeneous: A uniform appearance, it’s one phase. (Salt, H2O, Air, Apple Juice, Soda) Heterogeneous: Has a non-uniform appearance, more than One phase/more than one layer. (Oil+vinegar, Fe+S) PHYSICAL PROPERTIES Physical Properties: anything that observable, measurable, related to senses is a physical property. (Length of a pen, the color of a shirt, smell of gas, freezing). Physical change: Is when the identity, or chemical makeup of the substance or object is preserved, isn’t compromised. H2O(l) —-> H2O(g) Chemical Property: ability or inability of a substance or object to undergo a chemical change or reaction. (Combustion of gas with air, baking a cake, Chemical Change: is when the identity of the property is changed. CH4 + O2 —-> CO2 + H2O INTERNATIONAL SYSTEM UNITS (SI) Quantity Unit Symbol Time Second S Length Meter m Mass Kilogram kg Quantity of Matter Mole n Temp. Kelvin K Volume Cubic Meter m cubed (L) Temperature: is the average kinetic energy of particles. It is the degree of warmth or coolness of an object. Multiplier prefixes: Prefix Symbol Value Tera T 10^12 11B = 10^12 bytes Giga G 10^9 1GB = 10^9 bytes Mega M 10^6 1MB = 10^6 bytes Kilo K 10^3 1Km = 1000 m base unit m,s,L,byte Deci d 10^-1 1dm = 10^-1m Centi c 10^-2 1cm = 10^-2m Mili m 10^-3 micro upside down n 10^-6 nano n 10^-9 Pico p 10^-12 “Dimensional Analysis” Start with the given quantity, use the unit path/conversion factor to cancel units until you get to the wanted quantity. Given Quantity ——> Wanted Quantity Cancel units How many nanoseconds are in 29 years? 29 years = 365 days/1 years = 24 hours/1 day = 60 min/1 hour = 60 seconds/1 min = 10^9 nanoseconds/1 second = 9.145 x 10^17 ns How many nm are in 125 km? 1.25 x 10^14 nm How many months are in 6.7 x 10^37 ms? 2.5 x 10^25 months Temperature units: Temp F T(F) = 1.8 T(C) + 32 C K T(K) = T(C) + 273.15 What is 98 F in C and K? C = 36.6 K = 309.82 What is the temp in F when it is 453 K F = 355.73 SIGNIFICANT FIGURES Significant figures only refer to measurements! 28 students ——> exact number 145 cars ——> no measurement, only count. Exact number. 1.2 m ——> 2 sig figs, since the number is a measurement. (PowerPoint Ch.1 folder) NON-ZERO INTEGERS: always count as significant figures (1234 has 4 sf) ZEROS: LEADING ZEROS: not sf TRAILING ZEROS: ambiguous without decimal point (100), significant after decimal point (2.00 - 3 sf) CAPTIVE ZEROS: are always sf (30.0809 has 6 sf) Sig fig rules in operations: + and -, least decimal points win. Multiplication and division, least number of sig figs win. 14.195 + 9.21 = 23.405 —> 23.41 192.1 - 22.17 = 169.93 —> 169.9 22.1 x 1.9 = 41.99 —> 42 193.2 / 22.3 = 8.66367713 —> 8.66 COMBINATION OF OPERATIONS Do not round-off any intermediates, but instead underline the digits that must be reported with correct number of sig figs. Round off the final answer. 08-20-19 DENSITY: obligated with (d) or with (p) = the ratio of mass to volume D= m/v , g/mL, g/cm^3, Kg/L, Kg/m^3 1mL=1cm^3 1000mL=1L D of H2O = 1.09/mL ——-> 1 mL of H2O weighs 1.09 g D of Au =19.69/cm^3 ———> this weighs 19.6 g (Refer to handwritten notes for more density) PLS memorize to memorize polyatomic anions END OF CH. 1 CH. 2: Atoms and Elements LAW of conservation of mass: mass is neither created nor destroyed. A + B = C A + B = C 4 + 4 = 8 10g of Calcite has 4.0g of calcium, how many grams of calcite contains 25 g of calcium? 25.0g Ca x 10.0g C /4.0 g Ca = 63 calcite (2 sf) LAW of Definite Proportions: all samples of a compound have the same proportions of their elements regardless of the source. H2O —> 11.2% by mass H —-> 88.8% by mass O Dalton’s Atomic Theory i) A compound/chemical is composed of tiny particles called atoms ii) All atoms of an element are identical (not valid now) iii) Atoms of different elements are different iv) Atoms of different elements combine together to form/to make different molecules v) In a chemical reaction, the atom of an element can not be converted to a different atom. CH4 + O2 —> CO2 + H2O (carbon remains the same) REACTIONS CHEMICAL: electrons are involved, identity of atoms remain the same before and after the reactions. C —-> C NUCLEAR: identity of elements/atoms change. H —-> He C —-> N The structure of an Atom: (Refer to handwritten notes) SUBATOMIC PARTICLES: Name Symbol Charge Mass in amu Mass in Kg proton p +1 1 1.672 x10^-27 neutron n 0 1 1.674 x10^-27 electron e -1 0 0.00091 x10^-27 As of today, there are 118 elements, 98 of them are from nature, the rest are manmade. 11 are gas, 3 are liquid, the rest are solid. Liquid elements are Br, Hg and Cp. MEMORIZE TABLE 3.5 IN CH. 3 Seven elements in nature are diatomic! H2, N2, O2, F2, Cl2, Br2, I2 ISOTOPES Isotopes: atoms of the same element that have different numbers of neutrons, different mass number. Sy = symbol of atom (Refer to handwritten notes) Atom gains: A+ is a cation } Both are charged atoms Atom loses: A- is an anion The number of electrons in a neutral atom is equal to the number of protons! % Abundance: indicates how much of each isotope exists in nature. For example, Carbon 12 is 99%, Carbon 13 is 1%, Carbon 14 only exists in trace amounts. Out of 100 Carbons in nature, 99 of them are Carbon 12. ATOMIC MASS Atomic mass: the average mass of all isotopes of an element in amu. (Report the atomic masses with 2 decimal points) What is the atomic mass of Cu if there are two isotopes for Cu? (Must show work) 63 Cu - mass: 62.9396 - abu% 69.17 } 63.55 amu 65 Cu - mass: 64.9278 - abu% 30.83 Boron has two isotopes with 10 B mass of 10.0129 amu and 11 B with mass 11.009 amu and it’s atomic mass is 10.811 amu what is the % abundance of each isotope? PERIODIC TABLE 08-22-19 Group 1 - Alkali Earth metals Group 2 - Alkaline earth metals Group 3 - Boron family Group 4 - C Family Group 5 - N Family } main group elements Group 6 - Oxygen Family Group 7 - Halogens Group 8 - Noble gases MOLES One mole of any substance/object, contains Avogadro’s number entities. (6.022 x 10 ^ 23) 1 mol Na atom —-> 6.022 x 10^23 Na atom 6.022 EE 22 2 mol H20 molecule ——> 2(6.022 x 10^23) = 12.044 x 10^23 Molecular weight is the sum of the atomic masses of all atoms in a molecule in amu. MW H2O: (2 x 1.008) +15.99 = 18.02 amu Molar mass is the mass of a mole of any substance in grams. MM is numerically the same as MW, but in grams. Molecular weight of water is 18.02 amu. 1 water molecule weighs 18.02 amu. MM H2O = 18.02 grams 1 mole of water (6.022 x 10 ^ 23) H2O molecules weighs 18.02 grams. What is the molecular mass and molar mass of K3PO4? Molar mass = 212.27 grams Molecular mass = 212.27 amu How many moles are in 7.50 x 10^24 H2O molecules? How many molecules are in .670 moles of H2O How many a. Moles b. Grams are in 2.9 x 10^22 NaOH molecules? (Refer to handwritten notes for answers/work) How many H atoms are in 25 grams of H2O How many grams of O are in 2.9 x 10^24 Na2Cr2O7 molecules? (MM = 261.97 g/mol) CHAPTER 3: Molecules, compounds, and chemical equations Atoms bond to each other to become more stable. Combining atoms together makes limitless number of different molecules. Chemical bond - attractive forces that hold atoms together in a molecule CHEMICAL BONDS Covalent Bond: occurs between two or more nonmetals. Molecules result from covalent bonds are called molecular compounds or covalent compounds. Covalent bond is formed when two nonmetals share electrons. (H2O, C6H12O6, CO2, CH4) Ionic Bond: Occurs between a metal and a nonmetal, or a metal and a polyatomic anion. Molecules that result from ionic bonds are called compounds or salts. (NaCl, Ca(NO3)2, K3PO4). An ionic bond is formed by electron transfer. Metals lose electrons, non-metals gain electrons. A+, B- are held together tightly. Metallic Bond: occurs only between metals. 08-27-19 3.6: Naming cont. molecular/covalent compounds a Molecular/covalent compound is composed of two or more nonmetals. A covalent bond is formed when nonmetals share electrons. In naming molecular compounds, we use prefixes according to the number of each element in the molecule. # of atoms prefix 1 MON 2 DI 3 TRI 4 TETRA 5 PENTA 6 HEXA 7 HEPTA 8 OCTA 9 NONA 10 DECA 11 UNDECA 12 DODECA 13 TRIDECA NAMING A MOLECULAR COMPOUND Write the name of the first nonmetal. Use prefix di, tri, tetra, according to the number of the first nonmetal. (NEVER USE PREFIX MONO FOR FIRST NM) Use prefix mono, di, tri, tetra, according to the number of the second nonmetal, followed by the name of the second nonmetal with suffix -ide. (Oxygen = oxide, Sulfur = sulfide, Chlorine = chloride, Phosphorus = phosphide, Nitrogen = nitride, Carbon = carbide) Any monatomic anion has the suffix -ide. CO2 —-> carbon dioxide N2O5 —-> dinitrogen pentoxide SF6 —-> Sulfur Hexafluoride CO —-> Carbon Monoxide PCl3 —-> Phosphorus Trichloride H2O —-> Water NH3 —-> Ammonium } common names only! CH4—-> Methane Cl2O —-> Dichlorine Monoxide 3.5: Naming Ionic Compounds Ionic compounds or salts, are composed of a metal and nonmetal, or a metal and a polyatomic anion. (Never ever never ever never ever never ever never ever use prefix mono, di, tri, etc. for ionic compounds. Monatomic anions have suffix -ide. O2- —-> Oxide Br- —-> bromide S2- —-> Sulfide N3- —-> Nitride The charge of monatomic anions is their group number in the periodic table subtracted from 8! Oxygen is in group 6. O2- Polyatomic anions must be memorized, name/formula/charge. PO3-4 —-> Phosphate NO-3 —-> Nitriate Do not memorize the metals. The charge of metals is according to it’s group number in the periodic table. Group 1, +1, group 2, +2, group 3, +3. Transition metals have variable charges. The charge of transition metals must be specified with a Roman numeral (I, II, III). Don’t use Roman numeral for groups 1, 2, and 3 metals. There are four transition metals that have fixed charges and we never use Roman numerals for dem. The rest of the transition metals and post transition metals must have Roman numeral in parentheses after their names. NAMING IONIC COMPOUNDS Write the name of the metal. If it is a transition metal with variable charges, specify its charge with a Roman numeral. Write the name of the nonmetal with appropriate suffix -ide or the entire name of the polyatomic anion. Swap and drop charges. Give the metals charge to the polyatomic anion and vice versa. If subscripts can be simplified then you must simplify them. (Refer to handwritten notes bitch). 09/03/19 MOLECULAR FORMULA Molecular Formula: shows types and number of each atom in a molecule. (H2O, C6H12O6) Empirical Formula: shows the simplest ratio of atoms in a molecule. (CH2 can either be mf - C2H4, C3H6, C4H8) How to determine the empirical formula and molecular formula from given data. (Handwritten notes)