LAB_02_SynthesisAlumDGCS09

LAB_02_SynthesisAlumDGCS09 - Pre-lab Exercise Synthesis of...

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1/09 DGC Pre-lab Exercise Synthesis of Alum Work out the following questions in your lab notebook James, a first semester General Chemistry student at SNU, reacted 0.495 g of aluminum foil with 25 mL of 1.5 M KOH solution. After the aluminum had dissolved James acidified the reaction mixture with 5 mL of 9 M H 2 SO 4 . When James cooled the acidified solution in an ice bath the Alum (KAl(SO 4 ) 2 12H 2 O) precipitated. After filtering the Alum and allowing it to dry at room temperature, James determined that he isolated 6.435 g of KAl(SO 4 ) 2 12H 2 O. 1 - Determine the number of moles of aluminum and KOH that are present at the start of the reaction. (See section 3.4 & 3.7 in text.) 2 - Using the balanced net ionic equation, determine whether aluminum or KOH is the limiting reactant. (See section 3.6 in text.) 3 - Determine the formula mass of KAl(SO 4 ) 2 12H 2 O. (See section 3.3 in text.) 4 - Determine the theoretical yield. (See section 3.5 in text.) 5 - Determine the percent yield. (See section 3.5 in text.) 6 - What are the most likely reasons that James did not obtain a 100% yield? 7 - Where are the recovered and left over chemicals to be placed?
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1/09 DGC Th e Synth e s i s of Pota ss ium Alum Introdu c tion: In this experiment you will synthesize a compound that will contain the elements potassium, aluminum, sulfur, hydrogen, and oxygen. The final product may be given the formula KAl(SO 4 ) 2 12H 2 O, where the 12 H 2 O molecules are called the waters of hydration. This is the first experiment of a series in which you will synthesize the compound and then determine its simplest formula using a variety of analytical techniques. One important factor in any chemical synthesis is the actual quantity of desired product obtained compared to the theoretical amount predicted on the basis of the stoichiometry of the reaction. The ratio of the mass of product obtained to the theoretical quantity, expressed as a percentage, is referred to as the "percent yield" or more simply the "yield".
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LAB_02_SynthesisAlumDGCS09 - Pre-lab Exercise Synthesis of...

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