UMD CHEM132 Final Exam Questions And Answers.

Chemical Formulas - Answer Represent a compound Molecular Formulas - Answer Shows the actual numbers and kinds of atoms in one molecule Empirical Formula - Answer Shows the smallest, whole number ratio of atoms to one molecule Determining the empirical formula of Zinc Chloride - Answer Dissolve a known mass of Zinc Chloride in a measured volume of water, then determine the zinc content of the resulting solution by titration Titration - Answer Measuring the the volume of a standardized (known concentration) solution required to completely react with a target substance in the solution being analyzed End Point/Equivalence Point - Answer An added indicator to the titration mixture, where the the indicator changes color when the exact volume of standardized solution needed to completely react with the sample has been added Equivalence Point - Answer When the number of moles of EDTA added exactly equals the number of moles of Zn2+ originally present Ethylenediaminetetraacetic Acid (EDTA) - Answer Reacts with may metal ions to produce stable metal-EDTA complexes, but for a particular metal ion to complex with EDTA depends on the pH of the reaction solution; solution pHs of 10 or greater are required in order for EDTA to complex with calcium, magnesium, and zinc ions in water, particularly when Eriochrome Black T (EBT) is the indeicator Reaction of EDTA with Zn2+ - Answer Zn2+ (aq) + EDTA4- (aq) → [ZnEDTA]2- (aq) Eriochrome Black T (EBT) - Answer Red in zinc solutions containing Zn2+ that is not complexed with EDTA; at the equivalence point, EBT turns blue marking the end point Calculate the mass of (compound) in the (designated volume) titrated sample - Answer Divide the starting mass of (ion) by the total solution volume to determine solution concentration (g/mL) then multiply result by the volume of the titrated sample