B\u00e0i 3 (trang 233 sgk H\u00f3a 12 n\u00e2ng cao):\u00a0C\u00f3 dung d\u1ecbch ch\u1ee9a \u0111\u1ed3ng th\u1eddi c\u00e1c cation Ba_{2+<\/sub>, NH4<\/sub>^{+<\/sup>, Cr3+<\/sub>. Tr\u00ecnh b\u00e0y c\u00e1ch nh\u1eadn bi\u1ebft s\u1ef1 c\u00f3 m\u1eb7t t\u1eebng cation trong dung d\u1ecbch<\/strong><\/p>\n}}

L\u1eddi gi\u1ea3i:<\/b><\/p>\n

L\u1ea5y m\u1ed9t \u00edt dung d\u1ecbch, nh\u1ecf v\u00e0o \u0111\u00f3 v\u00e0i gi\u1ecdt kali \u0111icromat th\u1ea5y xu\u1ea5t hi\u1ec7n k\u1ebft t\u1ee7a m\u00e0u v\u00e0ng => C\u00f3 Ba_{2+<\/sub><\/p>\n}

2Ba_{2+<\/sub>\u00a0+ Cr2<\/sub>O7<\/sub>^{2-<\/sup>\u00a0+ H2<\/sub>O \u2192 2BaCrO4<\/sub>\u00a0+ 2H+<\/sup><\/p>\n}}

L\u1ea5y m\u1ed9t l\u01b0\u1ee3ng dung d\u1ecbch kh\u00e1c nh\u1ecf t\u1eeb t\u1eeb dung d\u1ecbch NaOH v\u00e0o, \u0111\u1eb7t tr\u00ean mi\u1ec7ng \u1ed1ng nghi\u1ec7m m\u1ed9t mi\u1ebfng gi\u1ea5y qu\u1ef3 t\u00edm \u1ea9m r\u1ed3i quan s\u00e1t :<\/p>\n

NH_{4<\/sub>^{+<\/sup>\u00a0+ OH–<\/sup>\u00a0\u2192 NH3<\/sub>\u00a0\u2191 + H2<\/sub>O<\/p>\n}}

NH_{3<\/sub>\u00a0m\u00f9i khai, l\u00e0m xanh qu\u1ef3 t\u00ednh<\/p>\n}

+ Trong dung d\u1ecbch xu\u1ea5t hi\u1ec7n k\u1ebft t\u1ee7a m\u00e0u xanh v\u00e0 tan d\u1ea7n, khi nh\u1ecf th\u00eam NaOH => C\u00f3 Cr_{3+<\/sub><\/p>\n}

Cr_{3+<\/sub>\u00a0+ 3OH^{–<\/sup>\u00a0\u2192 Cr(OH)3<\/sub>\u00a0\u2193 xanh<\/p>\n}}

Cr(OH)_{3<\/sub>\u00a0+ OH^{–<\/sup>\u00a0\u2192 [Cr(OH)4<\/sub>]<\/p>\n}}

B\u00e0i 4 (trang 233 sgk H\u00f3a 12 n\u00e2ng cao):\u00a0C\u00f3 dung d\u1ecbch ch\u1ee9a \u0111\u1ed3ng th\u1eddi c\u00e1c cation Ca^{2+<\/sup>, Al3+<\/sup>, Fe. Tr\u00ecnh b\u00e0y c\u00e1ch nh\u1eadn bi\u1ebft s\u1ef1 c\u00f3 m\u1eb7t t\u1eebng cation trong dung d\u1ecbch<\/strong><\/p>\n}

L\u1eddi gi\u1ea3i:<\/b><\/p>\n

L\u1ea5y m\u1ed9t \u00edt dung d\u1ecbch, nh\u1ecf v\u00e0o \u0111\u00f3 v\u00e0i gi\u1ecdt amoni thioxianat NH4SCN th\u1ea5y dung d\u1ecbch nhu\u1ed1m m\u00e0u \u0111\u1ecf m\u00e1u => c\u00f3 Fe^{3+<\/sup>.<\/p>\n}

Fe^{3+<\/sup>\u00a0+ 3SCN–<\/sup>\u00a0\u2192 Fe(SCN)_{3<\/sub>\u00a0m\u1ea7u \u0111\u1ecf.<\/p>\n}}

Nh\u1ecf t\u1eebng gi\u1ecdt NaOH v\u00e0o dung d\u1ecbch th\u1ea5y xu\u1ea5t hi\u1ec7n k\u1ebft t\u1ee7a \u0111\u1ecf n\u00e2u l\u1eabn v\u1edbi k\u1ebft t\u1ee7a tr\u1eafng, l\u1ecdc l\u1ea5y k\u1ebft t\u1ee7a, ti\u1ebfp t\u1ee5c nh\u1ecf NaOH th\u1ea5y l\u01b0\u1ee3ng k\u1ebft t\u1ee7a gi\u1ea3m d\u1ea7n. cu\u1ed1i c\u00f9ng ch\u1ec9 c\u00f2n l\u1ea1i k\u1ebft t\u1ee7a n\u00e2u => c\u00f3 Al^{3+<\/sup>.<\/p>\n}

Fe^{3+<\/sup>\u00a0+ 3OH–<\/sup>\u00a0\u2192 Fe(OH)_{3<\/sub>\u00a0m\u00e0u n\u00e2u<\/p>\n}}

Al^{3+<\/sup>\u00a0+ 3 OH–<\/sup>\u00a0\u2192 Al(OH)_{3<\/sub><\/p>\n}}

Al(OH)_{3<\/sub>\u00a0+ OH^{–<\/sup>\u00a0\u2192[Al(OH)4<\/sub>]–<\/sup><\/p>\n}}

Dung d\u1ecbch sau khi l\u1ecdc b\u1ecf k\u1ebft t\u1ee7a \u0111em axit h\u00f3a \u0111\u1ebfn m\u00f4i tr\u01b0\u1eddng pH t\u1eeb 4 \u2192 5 r\u1ed3i nh\u1ecf v\u00e0o \u0111\u00f3 dung d\u1ecbch (NH_{4<\/sub>)2<\/sub>C2<\/sub>O4<\/sub>\u00a0th\u1ea5y c\u00f3 xu\u1ea5t hi\u1ec7n k\u1ebft t\u1ee7a tr\u1eafng => C\u00f3 Ca^{2+<\/sup><\/p>\n}}

Ca^{2+<\/sup>\u00a0+ C_{2<\/sub>O4<\/sub>2-<\/sup>\u00a0\u2192 CaC2<\/sub>O4<\/sub>\u00a0\u2193<\/p>\n}}

V\u1eady dung d\u1ecbch ban \u0111\u1ea7u c\u00f3 Fe^{3+<\/sup>, Al3+<\/sup>, Ca2+<\/sup>.<\/p>\n}

B\u00e0i 5 (trang 233 sgk H\u00f3a 12 n\u00e2ng cao):\u00a0C\u00f3 dung d\u1ecbch ch\u1ee9a \u0111\u1ed3ng th\u1eddi c\u00e1c cation Ni^{2+<\/sup>Al3+<\/sup>, Fe3+<\/sup>. Tr\u00ecnh b\u00e0y c\u00e1ch nh\u1eadn bi\u1ebft s\u1ef1 c\u00f3 m\u1eb7t t\u1eebng cation trong dung d\u1ecbch<\/strong><\/p>\n}

L\u1eddi gi\u1ea3i:<\/b><\/p>\n

– Nh\u1ecf dung d\u1ecbch NH_{3<\/sub>\u00a0v\u00e0o dung d\u1ecbch th\u1ea5y c\u00f3 h\u1ed7n h\u1ee3p k\u1ebft t\u1ee7a tr\u1eafng xanh. L\u1ecdc l\u1ea5y k\u1ebft t\u1ee7a chia 3 ph\u1ea7n b\u1eb1ng nhau:<\/p>\n}

+ Ph\u1ea7n 1 \u0111\u1ec3 trong kh\u00f4ng kh\u00ed th\u1ea5y k\u1ebft t\u1ee7a d\u1ea7n chuy\u1ec3n sang m\u00e0u \u0111\u1ecf n\u00e2u => trong h\u1ed7n h\u1ee3p k\u1ebft t\u1ee7a c\u00f3 Fe(OH)_{2<\/sub>\u00a0v\u00e0 dung d\u1ecbch c\u00f3 Fe^{2+<\/sup><\/p>\n}}

Fe^{2+<\/sup>\u00a0+ 2NH_{3<\/sub>\u00a0+ 2H2<\/sub>O \u2192 Fe(OH)2<\/sub>\u00a0+ 2NH4<\/sub>+<\/sup><\/p>\n}}

4Fe(OH)_{2<\/sub>\u00a0+ 2H2<\/sub>O + O2<\/sub>\u00a0\u2192 4Fe(OH)3<\/sub><\/p>\n}

+ Nh\u1ecf v\u00e0o ph\u1ea7n 2 dung d\u1ecbch NH_{3<\/sub>\u00a0cho t\u1edbi d\u01b0, th\u1ea5y c\u00f3 m\u1ed9t ph\u1ea7n k\u1ebft t\u1ee7a m\u00e0u xanh tan ra v\u00e0 t\u1ea1o dung d\u1ecbch c\u00f3 m\u00e0u xanh => c\u00f3 Ni^{2+<\/sup><\/p>\n}}

Ni^{2+<\/sup>\u00a0+ 2NH_{3<\/sub>\u00a0+ 2H2<\/sub>O \u2192 Ni(OH)2<\/sub>\u00a0\u2193 xanh + 2NH4<\/sub>+<\/sup><\/p>\n}}

Ni(OH)_{2<\/sub>\u00a0+ 6NH3<\/sub>\u00a0\u2192 [Ni(NH3<\/sub>)6]^{2+<\/sup>m\u1ea7u xanh + 2OH–<\/sup><\/p>\n}}

+ Nh\u1ecf v\u00e0o ph\u1ea7n 3 dung d\u1ecbch NaOH, ph\u1ea7n k\u1ebft t\u1ee7a m\u00e0u tr\u1eafng tan ra t\u1ea1o dung d\u1ecbch kh\u00f4ng m\u00e0u => k\u1ebft t\u00f9a tan ra l\u00e0 Al(OH)_{3<\/sub>\u00a0v\u00e0 trong dung d\u1ecbch ban \u0111\u1ea7u c\u00f3 Al^{3+<\/sup><\/p>\n}}

Al^{3+<\/sup>\u00a0+ 3NH_{3<\/sub>\u00a0+ 3H2<\/sub>O \u2192 Al(OH)3<\/sub>\u00a0+ 3NH4<\/sub>+<\/sup><\/p>\n}}

Al(OH)_{3<\/sub>\u00a0+ OH^{–<\/sup>\u00a0\u2192 [Al(OH)4<\/sub>]–<\/sup><\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"}}

B\u00e0i 1 (trang 233 sgk H\u00f3a 12 n\u00e2ng cao):\u00a0C\u00f3 5 dung d\u1ecbch ri\u00eang r\u1ebd. M\u1ed7i dung d\u1ecbch ch\u1ee9a 1 cation sau \u0111\u00e2y: NH4+, Mg2+\u00a0Fe2+, Fe3+, Al3+, n\u1ed3ng \u0111\u1ed9 kho\u1ea3ng 0,1 M. B\u1eb1ng c\u00e1ch d\u00f9ng dung d\u1ecbch NaOH cho l\u1ea7n l\u01b0\u1ee3t v\u00e0o t\u1eebng dung d\u1ecbch, c\u00f3 th\u1ec3 nh\u1eadn bi\u1ebft t\u1ed1i \u0111a \u0111\u01b0\u1ee3c m\u1ea5y dung d\u1ecbch: A. […]<\/p>\n","protected":false},"author":3,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_mi_skip_tracking":false,"tdm_status":"","tdm_grid_status":""},"categories":[1306],"tags":[1429,1430],"yoast_head":"\n