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* Mr. Kinton Honors Chemistry * What’s a Mole? * The mole allows us to quantitatively understand how chemical reactions take place * Before we begin we need to examine some quantitative values pertaining to reactions * *Atoms of the same element (same # of protons), but with different numbers of neutrons. *Have different mass numbers (and masses) *Isotopes behave the same chemically because they still have the same number of protons and electrons * Subatomic 12C Particles 13C 14C Protons 6 6 6 Electrons 6 6 6 Neutrons 6 7 8 * * The actual masses of protons, neutrons and electrons are all very small * Therefore, we compare the relative masses of atoms * All relative to a reference isotope as a standard * Scientists picked Carbon-12 as the reference isotope * Carbon-12 has a standardized mass of 12 amu (atomic mass units) * *The weighted average mass of the atoms in a naturally occurring sample of the element ***Have to take isotopes and their relative abundances into account * Element X has 2 natural isotopes. The isotope with a mass of 10.012amu (10X) has a relative abundance of 19.91%. The isotope with a mass of 11.002amu (11X) has a relative abundance of 80.09%. Calculate the atomic mass of this element. Atomic mass= (m1)*(abundance1)+(m2)*(abundance2) 100 * * Which isotope of copper is more abundant: copper-63 or copper-65? * * An element is just its atomic weight * F2- (2 x 19.00)= 38.00 amu * K- 39.10 amu * The sum of the atomic weights of each atom * H2SO4(aq)- (2 x 1.008) + (32.07) + (4 x 16.00)= 98.09 amu * * Applies specifically to * Applies specifically to * C6H12O6- (6 x 12.01) + (12 x * NaCl- 22.99 + 35.45 = 58.44 compounds containing only nonmetals 1.008) + (6 x 16.00) = 180.2 amu * Units are in amu * compounds containing metals and nonmetals amu * Units are in amu * Calculate the formula weight of each compound and identify if it as a formula unit or a molecular weight: * C12H22O11 * Ca(NO3)2 * Al(OH)3 * CH3OH * * Amount of matter that contains as many objects as 12g of Carbon-12 * Avogadro’s Number- 6.02 x 1023 (molecules, atoms, ions, particles) * 1 mole Carbon-12 atoms = 6.02 x 1023 atoms * 1 mole of H2O molecules = 6.02 x 1023 molecules * 1 mole NO3- ions = 6.02 x 1023 ions * * A mole is always 6.02 x 1023 * The mass of a mole can be different * 1 atom of Carbon-12 has a mass of 12 amu * 1 mol of Carbon 12 has a mass of 12g * 1 atom of Magnesium-24 has a mass of 24 amu * 1 mol of Magnesium-24 has a mass of 24g * Given in g/mol * Has the same numerical value as the formula weight * H2O = 18.02 g/mol * Na = 22.99 g/mol * Ca(NO3)2 = 164.1 g/mol * * Calculate the molar mass of the following: * Ag * I2 * CO2 * Fe2O3 * * How many atoms are in 3g of Cu? * 3g Cu 1 mol Cu 6.02 x 1023 Cu atoms 63.5g 1 mole * 3 x 1022 Cu atoms * How many grams are in 4.01 x 1022 molecules of HNO3 * 4.01 x 1022 molecules 1 mole 63.02g 6.02 x 1023 1 mole * 4.20 g * * How many moles are in 5.380g of C6H12O6 * 5.380g 1 mol 180.16g * 0.02986mol * How many grams are in .433 mol Ca(NO3)2 * .433 mol 164.1g 1 mol * 71.1g * * Using dimensional analysis determine the following quantities: * Grams of NaHCO3 in 6.33 mol * Moles of H2SO4 in 2.9 x 10-3g * Atoms of Oxygen in 4.20g of HNO3 * Moles of C6H12O6 in 1.75 x 1022 molecules * * Percent mass contributed by each element * Comparison between calculated and theoretical values * Let’s examine glucose or C6H12O6 * * Calculate the percent composition of Nitrogen in Ca(NO3)2: * * Tells the relative number of atoms in a compound * Use percentages to determine the number of atoms of each element * Empirical formulas always contain the lowest whole number ratios of atoms * * 1. Mass % of elements * 2. Grams of each element * 3. Moles of each element * 4. Divide by small to get the Empirical formula * Ascorbic Acid contains 40.92% C, 4.58% H, and 54.50% O by mass. Determine the empirical formula * * Always a whole number multiple of the empirical formula * Must know the molecular weight * Ex) The empirical formula of mesitylene is C3H4. It has a molecular weight of 121 amu. What is it’s molecular formula * * Relationship among the quantities of reactants and products in a chemical reaction * Based on dimensional analysis * Mass to Moles * Particles to Moles * * 2H2 + O2 2H2O * Each coefficient tells us the number of moles * Since this tells us the number of moles we can convert between quantities of different substances * Calculate the amount of CO2 produced by the combustion of 1.00 g of butane * * Reactant that is completely consumed in a chemical reaction * Determines the amount of product formed * Quantity of product formed by the limiting reactant * Percent Yield: relates the actual yield to the theoretical yield * * What is the mass of 2.50 moles of oxygen gas? * How many moles are in 1.204 x 1025 molecules of SO3? * How many liters of gas do you have in .25 moles? *