Acids, Bases, and Buffers 2: Unknown Solutions Overview Getting Started Techniques Procedure FAQ Full Lab Manual Introduction & Goals Chemistry & Background Key Questions Prelab Problems Safety Procedure In Your Write-up Appendix Experiments Index ChemLab Home		Goals This week you will use the skills and knowledge gained in the last experiment to determine the acid-base character of two unknown samples. You and your partner will choose two different samples that are either an acid, a base, or a buffer. You will devise a procedure to determine what types of solutions you have and what their components are. A list of possible acids and conjugate acids of possible bases is given in the table on the Chemistry page. Buffers could be composed of any tabulated acid and its conjugate base. To Learn or Review Properties of Acids and Bases, pH Zumdahl, pp. 226-228, 241-251 Strength of Acids and Bases, pKa and pKb Zumdahl, pp. 229-233 Indicators Zumdahl, pp. 309-314 Buffers Zumdahl, pp. 279-287 Titration Curves and Polyprotic Acids Zumdahl, pp. 314-319 Introduction This week, you will use the skills and knowledge gained in the last experiment to determine the acid-base character of two unknown samples. You and your partner will choose two different samples that are either an acid, a base or a buffer. You will devise a procedure to determine what types of solutions you have and what their components are. A list of possible acids and conjugate acids of possible bases is given in Table 1 on page 149 of your manual. For each of your unknown samples you will need to answer the following questions: • Is it an acid, base, or buffer? • If an acid, what is the pKa? If it is a base, what is the pKb and the pKa of its conjugate acid? If it is a buffer, what is the pH and the buffer capacity for acid and for base? • For acids and bases, what is a likely identity of the unknown and what is the concentration of the solution, to three significant figures? For buffers, what is a likely identity of the acid and conjugate base present in the buffer and what is the ratio of acid to conjugate base in the solution?
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