【答案】2NH
4Cl+Ca(OH)
2CaCl
2+2NH
3↑+2H
2O;分液漏斗;取最后一次洗滌后的濾液少許于試管中,先加入稀硝酸酸化,再滴加硝酸銀溶液(或硝酸酸化的硝酸銀溶液),若無(wú)白色沉淀生成,則說(shuō)明已經(jīng)洗滌干凈;根據(jù)反應(yīng)的離子方程式:CaO
2+4H
++2I
-═Ca
2++2H
2O+I
2,I
2+2S
2O
32-→2I
-+S
4O
62-,可得關(guān)系式CaO
2~2S
2O
32-,n(Na
2S
2O
3)=0.200mol?L
-1×20.00mL×10
-3=0.004mol,由關(guān)系式“CaO
2?8H
2O~I(xiàn)
2~2S
2O
32-”可知,n(CaO
2?8H
2O)=0.5×0.004mol=0.002mol,m(CaO
2?8H
2O)=0.002mol×216g?mol
-1=0.432g,則樣品中CaO
2?8H
2O的質(zhì)量分?jǐn)?shù)為:ω(CaO
2?8H
2O)=
×100%=86.4%