实验设计——氯化铵的制备.doc

The Production of NH4ClPurposes(1) to master some fundamental operation of performing an experiment.(2) to confirm the relation of the solubility of salt and temperature.(3) to master the method to determine the percentage yield of nitrogen.Principles(1) 2NaCl + (NH4)2SO4 Na2SO4 + 2 NH4Cl(2) solubility dataT /0102030405060708090100NaCl35.735.83636.236.536.837.337.638.138.639.2(NH4)2SO470.67375.4788184.88891.695.399.2103.3Na2SO410H2O4.79.120.441/Na2SO4/49.748.246.745.244.143.342.742.3NH4Cl29.733.337.241.445.850.455.260.265.671.377.3(3) NH4Cl 12(NH4)2SO4 53.5u 66u 20 g 25 gm(NH4)2SO4 = M(NH4)2SO4 m(NH4Cl) / M(NH4Cl) = 66 20 / 53.5 25 (g)(4) NH4Cl NaCl 53.5u 58.5u 20 g 22 gm(NaCl) = M(NaCl) m(NH4Cl) / M(NH4Cl) = 58.5 20 / 53.5 22 (g)(5) Based on the solubility data, the water needed should just dissolve 22g NaCl and 25g (NH4)2SO4When the temperature is 20,NaCl H2O36 g 100 g22 g 61 gV(H2O) = m(H2O) /(H2O) = m(H2O) m(NaCl) / m(NaCl) (H2O) 61mL(NH4)2SO4 H2O 75.4 g 100 g 25 g 33 gV(H2O) = m(H2O) /(H2O) = m(H2O) m(NH4)2SO4 /m(NH4)2SO4 (H2O) 33mL61mL 33mLSo about 61mL distilled water is needed to dissolve the salt. To ensure that NaCl can dissolve completely, we should add 70mL 80mL distilled water into the beaker(6) the mixed solution should be heated until the solution is about 65mL-to avoid the crystallization of NaCl. Because the solubility of Na2SO4 decreases when temperature goes up, so when the solution is heated, Na2SO4 crystallizes.(7) the solution should be cooled to about 33 because the solubility of Na2SO410H2O and Na2SO4 are both the highest at about 32.4 according to the solubility data. Then they would not mix with NH4Cl.(8) the method of the examination of NH4Cl is heating. NH4Cl NH3+ HClWe can see that pure NH4Cl can be turned into gas and have no solid left when heated. The possible impurity cannot be turned into gas by this way. So this is the method to determine the purity of NH4Cl.The sketch of proceduresNa+ Cl- NH4+ SO42-NaCl solution25g NH4Cl22g NaCl70mL 80mL distilled water being heated and stirred to dissolve being bath heated, stirred to dissolve being bath heated,stirred and filtered by suction filtration Na+, Cl-, NH4+, SO42-NH4ClNa+, Cl-, NH4+, SO42-Na+, Cl-, NH4+, SO42-Na2SO4being cooled to about 33 and filtered by suction filtrationbeing bath heated, stirred and filtered by suction filtrationNa+, Cl-, NH4+, SO42-Na2SO4 being cooled to about 33 and filtered by suction filtrationNH4Clbeing bath heated, stirred and filtered by suction filtrationNa+, Cl-, NH4+, SO42-Na2SO4being cooled to about 33 and filtered by suction filtrationNa+, Cl-, NH4+, SO42-NH4ClNH4Cl being weighedMaterialsdistilled water, NaCl, (NH4)2SO4beaker, glass rod, Erlenmeyer flask, Buchner funnel, suction flask, Bunsen burner, tripod, graduated cylinder, spatula, weighting paper, filter paper, scale, match, thermometerProcedures(1) weigh 22g NaCl and measure 70mL 80mL distilled water, then mix them in a beaker.(2) heat the beaker while stirring to dissolve NaCl.(3) weigh 25g (NH4)2SO4 and add it into the beaker.(4) heat the beaker by bath heating while stirring.(5) mark the beaker by the place of 65mL.(6) concentrate the solution to about 65mL.(7) filter the mixture by suction filtration when the mixture is still hot.(8) cool the filtrate to about 33 . (9) filer the filtrate by suction filtration and collect the precipitate.(10) repeat procedure (7) to (9) two times.(11) weigh the precipitate and calculate.Points for Attention(1) before filtering the mixture by suction filtration when the mixture is still hot, the related instruments should be heated(2) the volume of the distilled water added in doesnt equal to the volume of the solution.(3) the mark of 65mL on the beaker should be made previously.Ref