Matter is made up of particles and a representative ...



REVIEWDimensional Analysis (Factor labeling)This is a problem solving method that focuses on units.It uses conversion factors that are equivalents like 2 pints = 1 quart and 60 seconds = 1 minute.MOST conversion factors have unlimited numbers of significant figures.You must practice using dimensional analysis – we will use it all year and failure to use it usually results in a wrong answer.THE UNITS MUST CANCEL – YOU MUST BE LEFT WITH THE UNITS YOU ARE SEEKING. WATCH SGINIFICANT FIGURES.SCIENTIFIC NOTATIONIf the number is less than one, move the decimal to the right. The exponent is negative and equals the number of places you moved the decimal point..00004567 4.567 x 10-5If the number is greater than one, move the decimal to the left. The exponent is positive.1234 1.234 x 1033. If the exponent is negative, move the decimal point to the left. The number is less than one.4.567 x 10-5 0.000045674. If the exponent is positive, move the decimal point to the right. The number is greater than one.1.234 x 103 1234SIGNIFICANT FIGURES1. Atlantic-Pacific RuleThis rule divides measurements into two kinds – those with a decimal point and those without. Imagine a map of the United States and superimpose the measurement on top. If a decimal point is present in the number, count significant digits from the Pacific side. (If decimal point is present, count from the Pacific side.) If a decimal point is absent, count from the Atlantic side.You should start counting with the first nonzero digit you find. Thereafter, all digits, including zero, are significant.2. Another Way 1. Digits other than zero are always significant.2. One or more final zeros used after the decimal point are always significant.3. Zeros between two other significant digits are always significant.4. Zeros used solely for spacing the decimal point are not significant. The zeros are place holders only.SC2. Students will relate how the Law of Conservation of Matter is used to determine chemical composition in compounds and chemical reactions.Apply concepts of the mole and Avogadro’s number to conceptualize and calculate? Mass, moles and molecules relationships,THE MOLECHAPTER 10IntroductionMatter is made up of particles. “Particle” is a generic term. You must look at the formula to determine what type of particle it is (atom, ion, molecule, etc.) (molecular) (ionic) Atoms MoleculesFormula unitsIons Fe H2O NaClSO4-2 He N2 CaCl2NH4+1You should be able to tell how many atoms are in each chemical formula. ATOMIC MASS, FORMULA MASS, and MOLECULAR MASSATOMIC MASSThis is the mass of an atom in atomic mass units (amu). It is the same as the average mass of the atoms of an element found on the periodic table.Example: C - single atom – 12.01 amuMOLECULAR MASSThis is the mass found by adding the atomic masses of the elements found in the molecule (molecular compound).Example: H2O – molecular compoundH (2 x 1.01amu) + O (1x16.00amu) = 18.02 amuFORMULA MASSThis is mass found by adding up the atomic masses of the elements found in a formula unit (ionic compound). Example: NaCl – ionic compoundNa (1 x 22.99amu) + Cl (1 x 35.45amu) = 58.44 amuDifferent atoms have different masses; THEREFORE different compounds have masses dependent upon the masses of the atoms that make them up.PRACTICE:Calculate the formula or molecular mass of the following compounds. Show your work correctly.A. H2SO4C. Al(NO3) 3B. C3H5N3O3D. Fe(CH3COO)3PERCENT COMPOSITIONChocolate Chip Cookies:450.0g sugar20.0mg saltLooking at the ingredients, what450.0g Crisco20.0mg baking sodapercentage of the total2 eggs (75.0g)20.0mg vanillacomposition is eggs?900.0g flourTo Calculate:Get the total amount (add up all the ingredients).Total = 450.0g + 450.0g + 75.0g + 900.0g + 0.002g + 0.002g + 0.002g = 1875.006g = 1875.0g320040012954000Find the percentage of the total that is eggs.part x 100 75.0g x 100 = 4.00 %total1875.0Practice:What is the mass percent of oxygen in H2SO4?THE MOLEThe MOLE (mol) is the unit of measurement used to describe the amount of matter in a particular substance. (Just like dozen, gross.) Also known as Avogadro’s number.1 mole = 6.0213672 x 1023 particles = 6.02 x 1023 particles (This is a rounded number.)(particles are atoms, ions, formula units, or molecules)MOLES TO MOLESThese kinds of problems involve making a comparison of one item to another. In one formula unit of Ca(OH)2 there is one atom of Ca, two atoms of O, and two atoms of H. If you have 2.0 moles of Ca(OH)2, then you would have 2.0 x 2 for the moles of O.1085850127635002.0 moles Ca(OH)2 2 mole O = 4.0 mol O 1 mol Ca(OH)2PRACTICEAlways start with the number you are given and then find the conversion factor that gets you to the desired outcome.How many moles of oxygen are in 3.4 moles of H2SO4?MOLES AND MASSThe mole is a conversion factor that relates the number of particles of matter to the matter’s mass. Molar mass = mass (g) of one mole of atoms. We will use dimensional analysis (factor label) to make mole/mass conversions. Example:All have 6.02x1023 atoms1 mole He = 4.00 g He1 mole Na = 22.99 g Na1 mole Mg = 24.31 g Mg1 mole Al = 26.98 g AlUse the conversion factor: atomicmolecular MASS (g) = 1 MOLE = MOLAR MASS formulaPRACTICE297180013906500A. Calculate the mass in grams of 2.0 moles of Na.102870013906500171450015303500205740010731500??g = 2.0 mol Na 22.99 g Na= g Na1 mol NaB. Calculate the mass in grams of 0.500 moles of CO2You can also calculate the number of moles in a given mass.C. How many moles are in 50.0 g of H2?125730012001500251460057150018288001600200020574008826500?? moles = 50.0 g H2 1 mole = mol H2 2.02g H2D. How many moles are in 75.0 g of NaOH?MOLES AND PARTICLESWe use factor label to make mole/particles conversions. Use the conversion factor: 1 mole = 6.02 x 1023 particles(particles are atoms, formula units, or molecules)PRACTICE:E. Determine the number of molecules in 2.23 moles of nitrogen, N2.114300063500003314700635000016002006350000?? molecules = 2.23 mol N2 6.02x1023 molecules N2 = molecules N22286000000 1 mol N2 Determine the number of atoms in 16.0 moles of sulfur.G. Determine the number of moles in 4.36 x 1024 atoms of silver, AgMASS AND MOLE AND PARTICLEYou can also convert mass to particles by going through moles. 1 mole 1 mole342900014668500137160014668500PARTICLES MOLEMASS(atoms, ions, 6.02 x 1023 molar mass (frommolecules, or funits) periodic table)Determine the number of atoms in 16.0 g of sulfur.160020010795000914400107950003886200514350027432007620000171450076200001143000196850021717003111500?? atoms = 16.0 g S 1 mol S 6.02x1023 atoms S = atoms S32.06 g S 1 mol SCalculate the number of grams in 1.20 x 1023 atoms of calcium. Calculate the number of molecules in 42.56g of water.SC2. Students will relate how the Law of Conservation of Matter is used to determine chemical composition in compounds and chemical reactions.Apply concepts of the mole and Avogadro’s number to conceptualize and calculate? Empirical/molecular formulas,EMPIRICAL FORMULAThe simplest whole number ratio of elements in a compound is called the EMPIRICAL FORMULA. In contrast, the molecular formula of a compound is the actual number of atoms of each element in the compound.The Empirical Formula can be calculated from the mole ratio or from percent composition data.Mole Ratio Example:What is the empirical formula for a compound if a 2.50 g sample contains 0.900 g of calcium and 1.60 g of chlorine?Step One – you must ALWAYS convert mass to moles:Determine the number of moles of Ca and Cl. (You must first determine the atomic mass of each.)20497802540000Ca0.900g Ca 1 mole Ca = 0.0225 mol 40.08g Ca19507201016000Cl1.60g Cl 1 mole Cl = 0.0451 mol 35.45g ClStep Two:To obtain the smallest ratio, divide both moles by the smaller number of moles (0.0225 mol).Ca 0.0225 mol = 1.00Cl 0.0451 mol = 2.00 0.0225 mol 0.0225 molStep Three:Look at the ratio of the two numbers. Round off to whole numbers (there are exceptions to this).Ca1.00becomesCa1The empirical formula is CaCl2Cl2.00becomesCl2PRACTICE:A. Find the empirical formula of the compound with 63.0g Rb and 5.90g O. Show your work correctly.Percent Composition Example:A compound has a percentage composition of 40.0% C, 6.71% H and 53.3% O. What is the empirical formula?Assume that there is 100 g (from 100%). In a 100g sample, there would be 40.0g C, 6.71g H, and 53.3g O. Then change the quantities to moles.Step One:14839951651000C40.0 g C 1 mole C = 3.33 mol C 12.01g C14839952286000H6.71 g H 1 mole H = 6.64 mol H 1.01g H14763751905000O53.3 g O 1 mole O = 3.33 mol O 16.00g O Step Two:To obtain the smallest ratio, divide both numbers of moles by the smaller number of moles (3.33 mol).C 3.33 mol = 1.00H 6.64 mol = 1.99O 3.33 mol = 1.00 3.33 mol 3.33 mol 3.33 molStep Three:Look at the ratio of the two numbers. Round off to whole numbers.C1.00becomesC1The empirical formula is CH2OH1.99becomesH2O1.00becomesO1PRACTICE:A. What is the empirical formula for a compound that has 32.8% Cr and 67.2% Cl?What happens when the mole ratios are not whole numbers?What is the empirical formula of a compound that contains 53.73% Fe and 46.27% S?MOLECULAR FORMULAIf you know the empirical formula of a substance and its mass, you can determine its molecular formula.EXAMPLEThe empirical formula of a substance is CH2O. The mass of the molecule is 180.0 amu. What is the molecular formula?Step One:Calculate the empirical mass for the empirical formula (CH2O) from the periodic table.C1 x 12.01 = 12.01H2 x 1.01 = 2.02O1 x 16.00 = 16.00 30.03 amu Step Two:Divide the molecular mass by the empirical mass.180.0 amu = 6.00030.03 amuStep Three:Multiply each element in the empirical formula by the number in step two to get the molecular formula.6 x CH2O C6H12O6So C6H12O6 is the molecular formula.PRACTICE:What is the molecular formula of a compound whose empirical formula is P2O3? The molecular mass of this compound is 220 g.HYDRATESDefine:Hydrates are solids with water molecules trapped in them. Used in the desiccation of substances and to store energy in solar cells. Usually have a specific ratio of water to the compound and are considered one single molecule.The “” does not mean to multiply. It means that waters are attached.The formula is written as:359473515621000(the number of waters)24288756985000XY XH2O (the formula) CuSO4 5H2O, copper (II) sulfate pentahydrateUse the same prefixes as with covalent compounds:mono – 1tri - 3penta – 5hepta -7nona -9di - 2tetra – 4hexa – 6octa - 8deca - 10Practice NamingNa3PO4 2H2O Ba(OH)2 8H2OSrCl2 6H2OANALYZING A HYDRATEIn order to analyze a hydrate, you must get rid of the water. This is usually done by heating the compound so that the water evaporates off. The compound that is left is “anhydrous” – without water. The compound usually changes color.DETERMINING THE HYDRATE’S FORMULAIt is a lot like calculating the empirical formula only you are not using single elements. You are using water and the compound. Follow these stepsYou have a 5.00g sample of a barium chloride hydrate. Determine the correct formula is you are given 5.00g of the hydrate and once you heat it and drive the water off, the new mass of the anhydrate is 4.26gStep One: Find the individual masses if they are not given to you. In this case, you need to find water.Hydrate mass – Anhydrate mass = water massExample: 5.00g – 4.26g = 0.74gStep Two: Find the empirical formula1270635128270004.26g BaCl2 1 mol BaCl2 = 0.0205mol BaCl2 208.23g BaCl21186815101600000.74g H2O 1 mol H2O = 0.041mol H2O 18.02g H2OStep Three: Divide the smallest mole amount into both.49968152921000BaCl20.0205mol = 1.00H2O 0.041mol = 2.00.0205mol 0.0250mol BaCl2 2H2OPractice:Determine the formula of a hydrate with 48.8% MgSO4 and 51.2% H2O ................
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