Experiment 1A.pdf - Experiment 1A CHEM 131 Qualitative Analysis of an Unknown Solution You should prepare for this experiment as usual First thoroughly

Experiment 1A.pdf - Experiment 1A CHEM 131 Qualitative...

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CHEM 131 Experiment 1A 1 CHEM 131 Experiment 1A Qualitative Analysis of an Unknown Solution You should prepare for this experiment as usual. First, thoroughly read this lab handout as well as sections 4.5 4.9 in your textbook. Then prepare your lab notebook by answering the prelab questions below, writing an introduction paragraph, drawing a procedure flowchart, and preparing a data table (refer to data tables in the report sheet for guidance). Finally, take the prelab quiz over the course website. As you conduct the experiment, record all of your observations in your lab notebook. Be sure to affix the label (sticker) from your unknown to the first of your lab notebook pages, and write the unknown number in the indicated location of the separate Experiment 1A Report Sheet. In addition to neatly transcribing your observational results onto the Report Sheet, you will write double-displacement reaction equations that accurately represent those observations, as well as a clear explanation of how you used your results to identify your unknown substance. Pre-lab Questions Predict what would happen if each set of substances below were mixed. In each case, (a) Write a balanced equation for any reaction that would occur. (b) Describe what you would observe if you carried out the reaction in the laboratory. If nothing would happen, simply write “no reaction.” 1. FeCl 3 ( aq ) + NaOH ( aq ) 2. KOH ( aq ) + HCl ( aq ) 3. K 2 CO 3 ( aq ) + AgNO 3 ( aq ) 4. K 2 SO 4 ( aq ) + BaCl 2 ( aq ) 5. BaCO 3 ( s ) + HNO 3 ( aq ) 6. Na 3 PO 4 ( aq ) + HNO 3 ( aq ) BACKGROUND Qualitative Analysis One of the most common tasks of a chemist is to determine the identity of a substance. We may wish to identify a contaminant in a water sample, determine the ores present in a rock sample, verify the product of a chemical synthesis, or diagnose anomalous compounds in the bloodstream. Any time that we try to identify a substance, we are performing a qualitative analysis . You will perform a qualitative analysis in this experiment.
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CHEM 131 Experiment 1A 2 In order to identify pure substances , we usually rely upon physical properties , such as color, melting point, density, etc., because these physical properties have unique, characteristic values. For mixtures , however, physical properties are less useful, and instead we rely upon either spectroscopic or chemical techniques of analysis. Spectroscopic (or spectrophotometric) techniques are based upon the unique quantized manner in which substances interact with energy of certain wavelengths (or colors). The flame test is in essence a crude spectroscopic technique that has been used in qualitative analysis for centuries. Modern spectroscopic analysis makes use of sophisticated electronic instruments (known as spectrophotometers). We will explore the principles and techniques of spectrophotometry in Experiment 4, midway through the semester.
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  • Spring '14
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