1.* 12.0 grams of salicylic acid were reacted with an excess of acetic anhydride and 11.0 grams of aspirin (acetylsalicylic acid) were obtained. Calculate the theoretical and percent yields of aspirin. \( \qquad \) 2. \( 25 \mathrm{~mL} \) of a \( 0.50 \mathrm{M} \mathrm{BaCl}_{2} \) solution is mixed with \( 25 \mathrm{~mL} \) of a \( 0.50 \mathrm{M} \mathrm{Na}_{2} \mathrm{CO}_{3} \) solution and 2.0 \( \mathrm{g} \) of \( \mathrm{BaCO}_{3} \) is collected. What is the percent yield of \( \mathrm{BaCO}_{3} \) ? \( \qquad \) 3. Double replacement reactions can be used in several ways to synthesize desired products. If the desired product is insoluble in water and two soluble reactants can be obtained that give the desired substance as one of the products, filtration can be used to isolate the product. For example, silver chloride could be prepared using the following reaction: \[ \mathrm{AgNO}_{3}(\mathrm{aq})+\mathrm{NaCl}\left(\text { (aq) }=\mathrm{AgCl}(\mathrm{s})+\mathrm{NaNO}_{3}(\text { (aq) }\right. \] If the desired product is soluble in water and two soluble reactants can be obtained that yield an insoluble product plus the desired product, evaporation of the filtrate will give the desired product. Stoichiometric amounts of the reactants must be used. For example, sodium nitrate could be prepared using the preceding reaction. Scanned with CamScanner 356 If an acid and a carbonate can be used, carbon dioxide, water and the desired product will be formed. If the product is soluble in water, stoichiometric amounts of the reactants must be used. For example, sodium sulfate could be prepared using the following reaction: \[ \mathrm{Na}_{2} \mathrm{CO}_{3}(\mathrm{aq})+\mathrm{H}_{2} \mathrm{SO}_{4}(\mathrm{aq})=\mathrm{H}_{2} \mathrm{O}(\mathrm{l})+\mathrm{CO}_{2}(\mathrm{q})+\mathrm{Na}_{2} \mathrm{SO}_{4}(\mathrm{qq}) \] If an acid and a base can be used, water and the desired product will be formed. If the product is soluble in water, stoichiometric amounts of the reactants must be used. For example, sodium sulfate could be prepared using the following reaction: \[ 2 \mathrm{NaOH}(\mathrm{aq})+\mathrm{H}_{2} \mathrm{SO}_{4}(\mathrm{aq})-2 \mathrm{H}_{2} \mathrm{O}(\mathrm{I})+\mathrm{Na}_{2} \mathrm{SO}_{4}(\mathrm{aq}) \] a. Why must stoichiometric amounts be used for the cases described above where the product is soluble in water? b. Why is the synthesis of sodium nitrate from silver nitrate suggested above of little value? Suggest pairs of reactants you could use in double replacement reactions to synthesize the compounds below. Include sufficient detail to make it clear how the product would be isolated (e.g., mix equal molar solutions of A and B, filter, evaporate the filtrate). Appendix 3 might be useful for this exercise. c.* calcium oxalate d. lithium iodide
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Silver sulfide, the tarnish on silver, comes from the reaction of silver metal with hydrogen sulfide and oxygen gas: 2Ag + H2S + O2 --> Ag2S + H2O Balance the equation. (3pts) How many grams of Ag2S can be formed from 496 g of Ag, 80.0 g of H2S, and 40.0 g of O2? (6pts) Which of the three reactants is the limiting reagent? Explain. (4pts) How many grams of the excess reactants are left over? (6pts) What was the actual yield of Ag2S if the percent yield is 78.9%? (3pts)
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