11th Class Chemistry Redox Reactions

  • question_answer 11) 1, 2 Assign oxidation number to the underlined elements in each of the following species: (a) \[\text{K}{{\underset{\text{-}}{\mathop{\text{I}}}\,}_{\text{3}}}\] (b) \[Ca{{\underset{-}{\mathop{O}}\,}_{2}}\] (c)\[Na{{H}_{2}}\underset{-}{\mathop{P}}\,{{O}_{4}}\] (d)\[{{H}_{4}}{{\underset{-}{\mathop{P}}\,}_{2}}{{O}_{7}}\] (e) \[Na\underset{-}{\mathop{B}}\,{{H}_{4}}\] (f) \[{{H}_{2}}{{\underset{-}{\mathop{S}}\,}_{2}}{{O}_{7}}\] (g)\[KAl{{(\underset{-}{\mathop{S}}\,{{O}_{4}})}_{2}}l2{{H}_{2}}O\] (h)\[{{H}_{2}}{{\underset{-}{\mathop{S}}\,}_{4}}{{O}_{6}}\] (i) \[\underset{-}{\mathop{C}}\,{{H}_{3}}\underset{-}{\mathop{C}}\,{{H}_{2}}OH\] (j) \[\underset{-}{\mathop{C}}\,{{H}_{3}}\underset{-}{\mathop{C}}\,OOH\]  

    Answer:

    (a) \[K{{\underset{-}{\mathop{I}}\,}_{3}}\] \[+1+3x=0\] \[x=-\frac{1}{3}\] (b) \[Ca{{\underset{-}{\mathop{O}}\,}_{2}}\] \[+2+2x=0\] \[x=-1\] (c) \[Na{{H}_{2}}\underset{-}{\mathop{P}}\,{{O}_{4}}\] \[+1+2+x-8=0\] \[x=+5\] (d) \[{{H}_{4}}{{\underset{-}{\mathop{P}}\,}_{2}}{{O}_{7}}\] \[+4+2x-14=0\] \[x=+5\] (e) \[Na\underset{-}{\mathop{B}}\,{{H}_{4}}\] \[+1+x+(-4)=0\] \[x=+3\] (f) \[{{H}_{2}}{{\underset{-}{\mathop{S}}\,}_{2}}{{O}_{7}}\] \[HO-\underset{\underset{O}{\mathop{\downarrow }}\,}{\overset{\overset{O}{\mathop{\uparrow }}\,}{\mathop{S}}}\,-O-\underset{\underset{O}{\mathop{\downarrow }}\,}{\overset{\overset{O}{\mathop{\uparrow }}\,}{\mathop{S}}}\,-OH\] \[+2+2x-14=0\] \[x=+6\] (g) \[KAl{{(\underset{-}{\mathop{S}}\,{{O}_{4}})}_{2}}.12{{H}_{2}}O\] \[+1+3+2(x-8)+12\times 0=0\] \[4+2x-16=0\] \[x=+6\] (h) \[{{H}_{2}}{{\underset{-}{\mathop{S}}\,}_{4}}{{O}_{6}}\] \[HO-O-\underset{\underset{O}{\mathop{\downarrow }}\,}{\overset{\overset{O}{\mathop{\uparrow }}\,}{\mathop{S}}}\,-S-S-\underset{\underset{O}{\mathop{\downarrow }}\,}{\overset{\overset{O}{\mathop{\uparrow }}\,}{\mathop{S}}}\,-O-H\] \[+2+4x-12=0\] \[x=+2.5\] The two donor sulphur atoms have +5 state, while non-donor atoms have zero oxidation state. (i) \[\underset{1}{\mathop{\underset{-}{\mathop{C}}\,}}\,{{H}_{3}}\underset{2}{\mathop{\underset{-}{\mathop{C}}\,}}\,{{H}_{2}}OH\,\,\,\,or\,{{\underset{-}{\mathop{C}}\,}_{2}}{{H}_{5}}OH\] Oxidation number of carbon \[=\frac{2{{n}_{O}}-{{n}_{H}}}{{{n}_{C}}}=\frac{2\times 1-6}{2}=-2\] \[\frac{\frac{\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }}{\text{Note:}\,\,\text{Carbon no}\text{. }\left( \text{1} \right)\text{ has }\left( \text{-3} \right)\text{ and carbon no}\text{. }\left( \text{2} \right)\text{ has }\left( \text{-1} \right)\text{ state}\text{.}}}{{}}\] (i) \[\underset{1}{\mathop{\underset{-}{\mathop{C}}\,}}\,{{H}_{3}}\underset{2}{\mathop{\underset{-}{\mathop{C}}\,}}\,OOH\,\,\,or\,\,{{C}_{2}}{{H}_{4}}{{O}_{2}}\] Oxidation number of carbon \[=\frac{2{{n}_{O}}-{{n}_{H}}}{{{n}_{C}}}=\frac{2\times 2-4}{2}=0\] \[\frac{\frac{\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }\!\!\_\!\!\text{ }}{\text{Note:}\,\,\text{Carbon no}\text{. }\left( \text{1} \right)\text{ has }\left( \text{-3} \right)\text{ and carbon no}\text{. }\left( \text{2} \right)\text{ has }\left( \text{+3} \right)\text{ state}\text{.}}}{{}}\]  


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