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UT Arlington CHEM 1465 - Molarity

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CHEM 1465 1st Edition Lecture 4Outline of Last Lecture 1. Chemical nomenclatureA. Molecular compoundsB. Ionic compounds2. Naming cationsA. Monoatomic cationsB. Transitional metalsC. Polyatomic cations 3. Naming anions A. Monoatomic anionsB. Polyatomic ending in “ide”C. OxoanionsD. Nitrate and sulfateE. Polyatomic anions 4. Naming ionic compounds A. Two important principlesB. Examples5. Hydrated ionic compoundsA. Common prefixes These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.B. Examples6. Chemical equationsA. Physical statesB. Balancing equationsOutline of Current Lecture 1. Aqueous solutions A. Solute and solventB. Water 2. The moleA. Number wordB. Molar massC. Mole to mole ratiosD. Chemical formulas E. Percent composition and empirical formula F. MolarityG. Dilution Current Lecture1. Aqueous solutions: solute must dissolve in a solvent A. Solute is the minor component and solvent is the major component B. Water as a solvent means you have an aqueous solution- Example is salt water where NaCl is solute and H2O is solvent 2. The mole: the SI unit for amount of substanceA. Mole is a number word- A dozen eggs= 12 eggs- Couple of tacos= 2 tacos- 1 mole of particles= 6.022x1023 particles- 1 mole of atoms= 6.022x1023 atoms- 1 mole of electrons= 6.022x1023 electrons-Example: how many moles of atoms are present in 9.5x1015 atoms?9.5x1015 atoms (1 mol6.022 x 1023) = 1.6x10-8 moles-Example: how many molecules are present in 2.35 mol of molecules?2.35 mol (6.022 x 10231 mol) = 1.42x1024 moleculesB. Mole relates to mass: molar mass (mass of one mole of substance)- Molar mass can be used to convert back and forth from grams to moles-1 mole of C = 12.01 grams C-1 mole of Na = 22.99 grams Na-1 mole of H2O = 18.02 grams H2O- Other terms for molar mass are molecular weight, formula mass, and formulaweight.- A very useful formula for molar mass is m=mass/n where n is the # of moles - Examples:-How many moles of carbon are in 25.0 grams of carbon?25.0 g C (1mol C12.01 g C) = 2.08 moles of carbon-How many iron atoms are in 675 g of iron?675 g Fe (1mol Fe55.85 g Fe) (6.022 x 10231 mol¿ = 7.28x1024 Fe atomsC. Mole to mole ratios can be found in two places- From the subscript of chemical formulas-magnesium nitrate Mg(NO3)2 means 1 mol Mg for every 2 mol NO3 and 6 molO for every 4 mol CO2- From the coefficients of balanced equations -2C2H6 + 7O2 → 4CO2 + 6H2O means 2 mol C2H6 for every 7 mol O2 and 7 mol O2 for every 4 mol CO2 and 6 mol H2O for every 4 mol CO2D. Chemical formulas - How many hydrogen atoms are in 59.3g of water?59.3g H2O (1mol H 2 O18.02 g H 2 O¿(2 mol H1 mol H 2O)(6.022 x 10231 mol H) = 3.96x1024 Hatoms- How many ions are in 3.99g of aluminum nitrate?3.99g (1 mol Al(NO 3)3213.0 g Al(NO3)3¿(3 mol N1 mol Al(NO3)3)(6.022 x 10231 mol N) = 3.38x1022ionsE. Percent composition and empirical formulas- Percent composition: percent by mass of each element in the compound - When finding the empirical formula, assume you have 100 grams of the compound so that the percent equals the number of grams- Example: a pure hydrocarbon is found to contain 85.7% carbon.C= 85.7 grams (1mol12.01 g¿= 7.14 moles of carbonH= 14.3 grams (1mol1.008 g¿ = 14.2 moles of hydrogen14.27.14=¿ 2 hydrogens for every 1 carbon The empirical formula is CH2F. Molarity is M= mol solute/ L solution- Example: what is the molarity of solution made by dissolving 25 grams of NaClO into 450 mL of water?25g NaClO (1 mol74.44 g¿→.336 moles of NaClO.336 mol NaClO.450 mL=¿ .75 MG. Dilution is MiVi = MfVf(adding solution doesn’t change amount of moles of solute)- Example: 65mL of solution is diluted to 250mL, what is the new concentration(molarity) if the initial molarity was .75M?65mL (.75M) = Mf (250mL)Mf = .20


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UT Arlington CHEM 1465 - Molarity

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