AP CHEMISTRY NOTES 1-1 MOLE FRACTION Mole Fraction (X) – the number of moles of a substance per total moles of a mixture Mole Fraction = ______Moles A________ Moles A + Moles B + . EXAMPLE: Determine the mole fraction of iodine in a mixture of 0.23 moles of I2 mixed with 1.1 moles of carbon tetrachloride (CCl4). EXAMPLE: A canister contains 2.3 g of PCl5, 1.2 g of PCl3, and 0.75 g of Cl2. Determine the mole fraction of each of these gases. AP CHEMISTRY NOTES 1-2 THE CONCENTRATION OF IONS IN SOLUTION REVIEW EXAMPLE: Determine the molarity of a solution that contains 1.22 g of KI dissolved in water to make 250. mL of solution. EXAMPLE: Determine the concentration of each ion in the following solutions: 0.25 M BaCl2 ___________________________________________________ 1.5 M Cr(OH)3 ___________________________________________________ 0.11 M K3PO4 ___________________________________________________ EXAMPLE: 100. mL of 0.50 M K2SO4 is mixed with 75.0 mL of 0.25 M Al(NO3)3. What is the concentration of each ion in the solution? EXAMPLE: 50. mL of 0.125 M FeCl3 is mixed with 25 mL of 0.220 M FeCl3. What is the resulting molarity of the solution? AP CHEMISTRY NOTES 1-3 THE PREPARATION OF SOLUTIONS BY DILUTION To Prepare a Solution by Dilution: M1 V1 = M2 V2 (stock soln) (new soln) EXAMPLE: How would you prepare 100.0 mL of a 0.40 M solution of MgSO4 from a stock solution that is 2.0 M in concentration? EXAMPLE: How much water would you add to 25 mL of 1.00 M NaOH to prepare a 0.75 M solution? AP CHEMISTRY NOTES 1-4 LIMITING REAGENTS REVISITED EXAMPLE: 20.0 grams of propane are reacted with 50.0 grams of oxygen at STP according to the following reaction: C3H8 + 5O2 → 3CO2 + 4H2O Determine the limiting reagent: Determine the mass of carbon dioxide produced: Determine the mass of excess reagent that remains after the reaction. AP CHEMISTRY NOTES 1-5 STOICHIOMETRY OF SOLUTIONS EXAMPLE: Calculate the volume of 12 M HCl that just reacts with 15 g of aluminum. EXAMPLE: What is the molarity of a solution of sodium hydroxide, NaOH, if 36.9 mL of this solution is required to react with 29.2 mL of 0.101 M hydrochloric acid solution according to the following reaction? __________ HCl + NaOH > NaCl + H2O AP CHEMISTRY NOTES 1-6 GRAVIMETRIC ANALYSIS EXAMPLE: An impure sample of solid Na2CO3 is allowed to react with 0.1755 M HCl. __________ Na2CO3 + 2HCl > 2NaCl + CO2 + H2O A 0.2337-g sample of sodium carbonate requires 15.55 mL of HCl solution to react completely. What is the purity of the sodium carbonate? EXAMPLE: When a sample of impure potassium chloride (0.4500g) was dissolved in water and treated with an excess of silver nitrate, 0.8402 g of silver chloride was precipitated. Calculate the percentage KCl in the original sample. AP CURRICULUM FRAMEWORK Unit 1 .