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Chemical Quantities and Aqueous Reactions

Chemical Quantities and Aqueous Reactions. Chapter 4. Stoichiometry. Disulfur dichloride S 2 Cl 2 , is used to vulcanize rubber. It can be made by treating molten sulfur with gaseous chlorine S 8 (l) + 4 Cl 2 (g)  4 S 2 Cl 2 (g)

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Chemical Quantities and Aqueous Reactions

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  1. Chemical Quantities and Aqueous Reactions Chapter 4

  2. Stoichiometry Disulfur dichloride S2Cl2, is used to vulcanize rubber. It can be made by treating molten sulfur with gaseous chlorine S8(l) + 4 Cl2(g)  4 S2Cl2(g) Calculate the mass of S2Cl2 that can be produced by reacting 15.0 g of S8 with excess chlorine gas. If 28.4 grams of S2Cl2 are produced, what is the percent yield? Practice problems Tro – 4.25-4.36

  3. Limiting Reagent • One of the steps in the commercial process for converting ammonia to nitric acid involves the conversion of NH3 to NO: • 4 NH3(g) + 5 O2(g)  4 NO(g) + 6 H2O(g) • How many grams of NO form when 1.50 g of NH3 reacts with 1.85 g of O2? • Which reactant is the limiting reactant and which is the excess reactant? • How much of the excess reactant remains after the limiting reactant is completely consumed? Practice problems Tro – 4.37-4.52

  4. Solution ConcentrationMass percent • (mass part/mass whole) x 100(%) • An aqueous solution of acetic acid is 20 percent by weight Acetic acid has a density of 1.0269 g/mL. How many moles of acetic acid are contained in 35 mL of this solution? Practice problem Tro – 4.55

  5. Solution ConcentrationMolarity (M) • Mole solute/ Liter solution • For Dilution -- M1V1 = M2V2 • A chemist wants to prepare 0.25 M HCl. Commercial HCl is 12.4M. How many mL of the concentrated acid does the chemist require to make up 1.50 L of the dilute acid? Practice problems Tro – 4.59-4.62

  6. Solution ConcentrationMolarity (M) • Conversion of % to molarity • A 35.0% solution of glucose (C6H12O6) has a density of 1.28 g/mL. What is the molarity of the solution? Practice problems Tro – 4.95-4.96

  7. Solution Stoichiometry • Some sulfuric acid is spilled on a lab bench. It can be neutralized by sprinkling sodium bicarbonate on it and then mopping up the resultant solution. The sodium bicarbonate reacts with sulfuric acid as follows: • 2NaHCO3(s) + H2SO4(aq)  Na2SO4(aq) + 2H2O(l) + 2CO2(g) • Sodium bicarbonate is added until the fizzing due to the formation of CO2(g) stops. If 27 mL of 6.0M H2SO4 was spilled, what if the minimum mass of NaHCO3 that must be added to the spill to neutralize the acid?

  8. Solution Stoichiometry • 581 mL of 0.342 M Barium nitrate [Ba(NO3)2] are mixed with 264 mL of 0.631 M potassium sulfate (K2SO4). Write the molecular, ionic, and net ionic reactions for this reaction, calculate the mass of any precipitate produced and inventory the ions in solution after precipitation. Practice problems Tro – 4.116

  9. A 35.49 mL sample of 0.2430 M H2SO4 is mixed with 65.33 mL of a 0.4199 M sample of KOH. Determine the concentration of all ions in solution, the pH, and pOH. Remember

  10. Titrations • A noncarbonated soft drink contains an unknown amount of citric acid, H3C6H5O7. If 100.0 mL of the soft drink requires 33.51 mL of 0.01024 M NaOH to neutralize the citric acid completely, what is the concentration of citric acid in the soft drink in moles/liter (M)? In equivalents/liter (N)? Practice problems Tro – 4.84, 4.110

  11. Titrations • Suppose you are given a 4.554 g sample that is a mixture of oxalic acid, H2C2O4, and another solid that does not react with sodium hydroxide. If 29.58 mL of 0.5501 M NaOH is required to titrate the oxalic acid in the 4.554 g sample, what is the weight percent of oxalic acid in the mixture?

  12. An unknown solid acid is either citric acid or tartaric acid. To determine which acid you have, you titrate a sample of the solid with aqueous NaOH and from this determine the molar mass of the unknown acid. A 0.956 g sample was titrated with 29.1 mL of 0.513 M NaOH. The formulas for the acids are • Citric acid H3C6H5O7 • Tartaric acid H2C4H4O6

  13. The molar mass of a certain metal carbonate, MCO3, can be determined by adding an excess of HCl acid to react with all the carbonate and then “back titrating” the remaining acid with a NaOH solution. • Write the equations for these reactions • In a certain experiment, 20.00 mL of 0.0800 M HCl were added to a 0.1022 g sample of MCO3. The excess HCl required 5.64 mL of 0.1000 M NaOH for neutralization. Calculate the molar mass of the carbonate and identify M.

  14. Challenge Problem • A 19.264 gram sample of a mixture of MgCl2 and CsCl is dissolved in water and treated with excess AgNO3 so that ALL the chloride precipitates as AgCl. The mass of dried AgCl is 43.668 grams. Calculate the mass CsCl in the sample.

  15. The compound aluminum chloride is widely used to control chemical reactions in industry. It is made by the following reaction: • Al2O3 + 3C + 3Cl2 2AlCl3 + 3 CO • How many grams of AlCl3 can be made from the reaction of 100. g Al2O3, 45 g C, and 160. gCl2?

  16. In 1978, scientists extracted a compound with antitumor and antiviral properties from tunicates in the Caribbean Sea. A 2.52 mg sample of the compound, didemnin-C, was analyzed and found to have the following composition; 1.55 mg C, 0.204 mg H, 0.209 mg N and 0.557 mg O. The mass spectrum of didemnin-C was found to have a parent peak at 1014 g/mol that represents the molar mass of the compound. What is the molecular formula of didemnin-C?

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