Conductivity Lab
Post-Lab Questions 1. Using the information provided in the Introduction and your observations from Part 1, hypothesize as to the type of electrolyte the following solutions would be. Justify the hypothesis from a chemical standpoint. a. Aqueous Sodium Hydroxide—NaOH (aq) is a very strong base, which will completely disassociate into Na+ and OH- ions, which would make it a very strong electrolyte. Chemical reaction of the disassociation of Sodium Hydroxide: NaOH (aq)Na+ (aq)+ OH-(aq) b. Aqueous NaCl—Sodium Chloride contains both sodium and chloride ions, but in the solid state they are locked in place and therefore unavailable to conduct electricity. But, when NaCl is dissolved in water, the ions are free to move and conduct electricity, making NaCl a strong electrolyte. Chemical reaction of the disassociation of Sodium Chloride: NaCl(aq)Na+ (aq)+ Cl-(aq) c. Aqueous Formic Acid—HCOOH, formic acid, is a weak electrolyte. This is due to its covalent bonds, but when added to water the acid releases some of ions that allow for little conductivity. The chemical reaction of the disassociation of Formic Acid:
HCOOH(aq) H+(aq) + COOH-(aq) d. Glacial Formic Acid—Despite being a liquid, glacial formic acid is a covalent compound in pure form; it cannot ionize and become an electrolyte until it is mixed with water. Adding water will allow very few of the glacial formic acid to ionize. Because there are so few ions present, solutions of these substances do not conduct electricity at all (or a very poor conductors at best), making Formic Acid a non-electrolyte. 2. Based on the titration results from Part 2, how would results differ in Na2SO4 was used to titrate Ba(OH)2? HINT: Determine the reaction between Na2SO4 and Ba(OH)2 –what would be the conducting species at the equivalence point? What type of electrolyte is that species? Sodium Sulfate is a strong electrolyte. When added to the Barium Hydroxide the titration process would happen much quicker
HCOOH(aq) H+(aq) + COOH-(aq) d. Glacial Formic Acid—Despite being a liquid, glacial formic acid is a covalent compound in pure form; it cannot ionize and become an electrolyte until it is mixed with water. Adding water will allow very few of the glacial formic acid to ionize. Because there are so few ions present, solutions of these substances do not conduct electricity at all (or a very poor conductors at best), making Formic Acid a non-electrolyte. 2. Based on the titration results from Part 2, how would results differ in Na2SO4 was used to titrate Ba(OH)2? HINT: Determine the reaction between Na2SO4 and Ba(OH)2 –what would be the conducting species at the equivalence point? What type of electrolyte is that species? Sodium Sulfate is a strong electrolyte. When added to the Barium Hydroxide the titration process would happen much quicker
Cited: 2"Experiment 1B: Analysis of Sulfuric Acid Solution." Marin.edu. N.p., n.d. Web. 24 Sept. 2012. <http://www.marin.edu/homepages/ErikDunmire/CHEM131/Experiment1B.pdf>. 1Graves, Dr. "Conductivity of Aqueous Solutions and Conductometric Titrations." General Chemistry I (Lab Manual). Ed. Vanessa Thompson. Miami: Florida International University, 2012. 55-60. Print. 3Pautz, R. "18 Conductometric Titration Lab Activity." Www.vrml.k12.la.us. Xplorer GLX, n.d. Web. 24 Sept. 2012. <http://www.vrml.k12.la.us/rpautz/documents/Chemistry/ConductometricTitration.pdf>. 4Senese, Fred. "How Can Ba(OH)2 Concentrations Be Determined Using H2SO4, HCl, and Na2SO4 Solutions?" General Chemistry Online: FAQ: The Mole Concept: How Can Ba(OH)_2_ Concentrations Be Determined Using H_2_SO_4_, HCl, and Na_2_SO_4_ Solutions? Gen Chem Online, 15 Feb. 2010. Web. 25 Sept. 2012. <http://antoine.frostburg.edu/chem/senese/101/moles/faq/baoh2-assay.shtml>.