Chemistry Weeks 1 and 2
Chemistry Weeks 1 and 2 CHE 105
Popular in Chemistry: Principles and Applications
Popular in Chemistry
This 8 page Bundle was uploaded by Catherine Carter on Monday August 29, 2016. The Bundle belongs to CHE 105 at University at Buffalo taught by Melvyn Churchill in Summer 2015. Since its upload, it has received 32 views. For similar materials see Chemistry: Principles and Applications in Chemistry at University at Buffalo.
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Date Created: 08/29/16
Chemistry 8/30/16 Matter and Measurement matter occupies space and has mass pure substances have definite composition and properties as well as a formula elements are made up of one thing compounds are made up of multiple element and are chemically bonded in fixed proportions atoms are the building blocks of matter Law of constant composition or definite proportions gas (no shape or volume), liquid (no shape but has volume), and solid (has both shape and volume) 118 known elements >82 are unstable an element is a substance that can’t be separated into simpler substances by chemical means about 90 elements occur naturally (up to 92 on the periodic table except 43&61) 28 newer elements were created by scientists including “missing” elements and more than 20 “transuranic elements” (93118) mixture 2 or more substances that retain their identities o homogenous same throughout o heterogeneous – is not the same throughout o In the graph Below the red line indicates no and the blue line indicates yes Homogenous Mixture Homogenous (Variable Element Composition?) Pure Substance Matter (Separated (Is it uniform?) Chemically?) Heterogeneous Compound Mixture Chemical Symbols of Common Elements indicated by a single capital of 2 letters with the first being a capital 9 single lettered nonmetals: H, B, C, N, O, F, P, S, I most are the first 2 letters Al, Ar, Li, Ca, He, Si, Ba, Br others are the first letter and a later letter Mg, Mn, Cl, Cr, Pt, Pd ten metals have symbols based on the latin name (one from the german) Cu, Au, Fe, Na, Ag, Sn, Pb, Hg, Sb, K, W Properties and Changes of Matter physical (density, mass, volume) chemical has to be changed to a different thing (flammability, corrosiveness, acid/base reactions) intensive properties of matter are independent of the amount of substance present exclusive properties of matter depends on amount of substance Separation of Mixture distillations – need different boiling points filtration chromatography most held to the paper moves more slowly/less, less stuck moves faster/farther Units of measurement being used: kilogram, meter, second, kelvin, mole Prefixes: Giga G 10^9 Milli a 10^3 Mega M 10^6 Micro µ 10^6 Kilo k 10^3 Nano n 1^9 Deci d 10^1 Pico p 10^12 Centi c 10^2 Femto f 10^15 K=℃+273.15℉=1.8 (℃ )+32℃=(5/9)(℉−32) Uncertainty in Measurement there is always going to be a degree of uncertainty which is why sigfigs matter (more than 9 is not truly accurate, there is no degree that certain) all nonzeroes are significant (zeroes mean something in between nonzeroes, before a number they are placeholders, if there are a lot of zeroes use scientific notation. zeroes at the end of a number matter but should write in scientific notation if there is no decimal place) when adding and subtracting answers are rounded to the least significant decimal place when multiplying and dividing you should round so that it has the same number of sigfigs as the one with the least amount of sigfigs try to always use scientific notation. Don’t need to worry about sigfigs with exact numbers m Density formula: d= V For combination problems do any addition and subtraction first, then multiply or divide o With adding numbers in scientific notation, make sure the exponents are the same Accuracy is how close to the true value you are Precision is if you can do the procedure the same way every single time Dimensional analysis (converting things without changing the value) o Units are important because you have to cancel out the old units to get the new units Chapter 2 Dalton’s Postulates o Each element is composed of extremely small particles called atoms o All atoms of a given element are identical in mass and properties but atoms of one element are different from all others o Atoms of an element are not changed into different atoms of a different element by chemical means. And atoms are neither created nor destroyed in chemical reactions o Compounds are formed when atoms of elements combine and a given compound always has the same number and types of elements Law of Constant Composition – the elemental composition of a pure substance never varies Law of Conservation of Mass – the total mass of substances present at the end of a chemical process is the same as the mass of substances present before the process took place (Some mass is lost if energy is produced but it is negligible) Law of Multiple Proportions – if two elements, A and B, combine to form more than one compound, then the masses of B which can combine with a fixed amount of A are in a ratio of small whole numbers Cathode rays = electrons (1.76 x 10^8 Coulombs/gram) Milliken’ oil drop experiment o Oil drops sprayed o They fell through a plate with a small hole o They gain a charge o An electrical field holds it up as gravity pulls it down so that it levitates o Then determined the charge on an electron: 1.60 x 10^19 C o Mass (today’s accuracy) : 9.10939 x 10^28 g Radioactivity o The spontaneous emission of radiation from the nucleus of an atom o particles (These are He2 nuclei) o particles (electrons, e – same as “cathode rays”) o rays (hν high energy electromagnetic radiation) Original model called the “Plum Pudding Model” until disproved by Rutherford’s Gold Foil Experiment o Most particles went through the gold foil but some were deflected, concluded atom was mostly empty space An atom has protons, nuetrons, and electrons o Mass comes from the nucleus Isotopes have a different number of nuetrons o Electrons create most of the volume Ions have different numbers of electrons o Nuetrons decay and produce protons and electrons Mass and charge is always balanced, even in nuclear reactions 24 1 amu = 1.66054 x 10 g = 1/12(mass of C12) A nuclide is a nucleus with a specified number of protons and neutrons Protons and neutrons are categorized as nucleons All atoms of the same element have the same number of protons which defines the atomic number The atomic number is equal to the electrons so that there is no net charge (unless it is an ion) The average atomic mass is used in calculations o It is the weighted mean of the masses o averagemass=Σ[ fractionalabundancexmass] o This is measured with a mass spectrometer The substance is set on one end, is sent through slits after being charged and then diverted by a magnetic field, heavier elements are bent by the field less than the lighter elements, they land in other slits that categorize the by what they are The periodic table o If listed by mass or protons(better) it shows the repeating patterns of the elements o It is systematic organization of the elements o Rows are called periods and columns are called groups o Elements in the same group have similar properties, these are known by these names: 1 alkali metals 2 alkaline earth metals 16 – chalcogens 17 – halogens 18 – noble gases 11 – coinage metals o Metals: lustrous, heat and electrical conductivity, solids at room temperature (except Hg) o Nonmetals: 5 solid at room temperature (C, P, S, Se, I), 1 is liquid (Br2), other 11 are gases, all poor thermal and electrical conductors (except graphite), solids are usually brittle o Metalloids: only 6 are commonly occurring and stable, have properties of both metals and nonmetals o Only noble gases exist as single atoms, most others exist as molecules Allotropes consist of 1 element with different number of atoms and each has different and distinct properties Diatomic Molecules – are always found paired with itself (BrINClHOF) Compounds that have discrete molecules are called molecular compounds, they have more than 1 element and are usually composed of nonmetals Subscript to the right tells you how many atoms of that element (no subscript means 1) Empirical formula gives the lowest number ratio of the atoms (you can’t determine the molecular formula from the empirical formula) Structural formula shows the connectivity of the atoms (how they’re bonded) Perspective formula – indicates stereochemistry (3D view) o Ball and stick (most useful) o Space filling (larger scale model of actual molecule) Ions – charged particle (from a loss of gain of electrons) o Cations are positive (lose electrons and shrinks in size) for naming: use normal name then say ion o Anions are negative (gain electrons and increase in size) for naming: change ending to ide then say ion o Polyatomic ions and molecules with net charges o Noble gases have a stable number of electrons o Unstable atoms are constantly trying to become stable o Most transition metals have multiple stable cations so which one is used is indicated by roman numerals after the name of the metal (Hg2 ^2+ is Mercury(I) because it is diatomic in the +1 state) Ionic compounds and a combination of metals and nonmetals and involve an electron transfer o Should be put in the simplest ratio o Naming For Ionic Compounds o write the unchanged name of the cation, then the anion if the anion is an element the ending changes to –ide, if it is a polyatomic ion the name stays the same if the cation has more than one state, indicate the proper state with roman numerals in parenthesis after the cation o for neutral compounds, the total charge must be zero o is usually between a metal and a nonmetal or a polyatomic ion Covalent Binary Compounds o involves two nonmetals o the less electronegative element is listed first a prefix is used to denote the number of atoms of each element of the compound mono is NEVER used for the first element the more electronegative atom is listed second and the ending is changed to –ide to determine electronegativity look at the table, it increases on a diagonal up to Fluorine o the exceptions are water, ammonia, phosphine (PH3), and methane (CH4) Naming Inorganic acids: oxoanions and oxoacids o oxoanions: when there are only two oxoanions involving the same element the one with the fewer oxygen atoms ends in –ite and the one with more ends in –ate nitrite and nitrate or sulfite and sulfate when there are four oxoanions involving the same element, the one with the second fewest oxygen atoms ends in –ite and the one with the second most ends in –ate, the one with the fewest has the prefix hypo and ends in –ite, the one with the most has the prefix per and ends in –ate hypochlorite (ClO^), chlorite (ClO2^), chlorate (Cl03^), perchlorate (ClO4^) Naming oxoacids if the anion ends in –ide change the ending to –ic acid and add the prefix hydro if the anion ends in –ate change the ending to –ic acid if the anion ends in –ite change the ending to –ous acid o with oxoacids, when you remove a hydrogen atom it becomes whatever the name of the anion is without the extra hydrogen (ex: Carbonic Acid (H2CO3) goes to hydrogen and hydrogen carbonate anion (HCO3^) which goes to the carbonate anion (CO3^2) Naming bases o simplest are soluble hydroxides, (basic oxides that reacted with water) where you say the name of the metal and add hydroxide to the end o for hydrates you say the name of the ionic compound and then a corresponding prefix (for the number of water molecules to react) attached to hydrate ions with nonsystematic names: o cations: H3O+, NH4+ o anions: hydroxide OH, cyanide CN, peroxide O2^2, superoxide O2^ Naming Organic (nonintensive) o carboxylic acids have one or more CO2H group (acetic acid (CH3CO2H) and oxalic acid (H2C2O4) o Organic compounds: alkanes contain only carbon and hydrogen (all single bonds) the prefix tells the number of carbon, then the number of hydrogen is the number needed to make all the carbon “full” (meth = 1, eth = 2, prop = 3, but = 4, pent = 5, hex = 6, hept = 7, oct = 8 ) when a hydrogen is replaced with something else an ending is added to the basic compound for –OH group it ends in –ol and that organic compound is an alcohol
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