有關化學REDOX REACTION(15分)

kelvin

2010-10-30 8:49 am

2Sr(NO3)2--------> 2SrO(s) + 4NO2(g)+ O2(g)
using oxidation numbers, explain why the reaction involves both oxidation and reduction.(3分)

唔該請詳細解釋 THZ

更新1:

唔該哂一樓個位　但係我仲有D野想問問你　NO2 係N 係+4 O係-2咁變左無CHARGE 因為O有2粒　但係我之前睇書NO2 應該係負CHARGE 係唔係即係係CHEMICAL REACTION入面只有結合物入面既元素先會有CHARGE? 同埋再想問問你 O2 唔係因為 -2+ (+2) [即係一粒OXYGEN 加第2粒OXYGEN而變成架咩?] 我明白N 係多左粒電子但係我唔多明點解係由DIOXYGEN 釋放比佢 DIOXYGEN 係無CHARGE 唔係因為 1個－2 既OXYGEN同一個＋二既ＯＸＹＧＥＮ結合而變成無ＣＨＡＲＧＥ咩？點解係會由佢送ＥＬＥＣＴＲＯＮ比　Ｎ？

更新2:

唔係因為 1個－2 既OXYGEN同一個＋２既ＯＸＹＧＥＮ結合而變成無ＣＨＡＲＧＥ咩？

回答 (1)

己式庚辛

2010-10-30 11:40 am

✔ 最佳答案

now look at the oxidation number of N and O.
before reaction, oxidation number of N in nitrate is +5, O is -2.

after reaction, O.N. of nitrogen in NO2 becomes +4, while O in dioxygen is 0.
nitrogen is reduced while oxygen is oxidized.

that should be enough to get all three marks.
to go into details...
nitrate NO3(-) has total charge of 1- ;
oxygen in nitrate has O.N. of -2, as like in most cases;
O.N. of nitrogen is (-1) - (-2)x2 = +5.

in NO2, oxygen has O.N. of -2;
nitrogen is 0 - (-2)x2 = +4;
dioxygen, as in elemental form, has O.N. of zero.

2010-10-31 04:41:15 補充：
NO2 is nitrogen dioxide gas; NO2(-) is nitrite ion. they're different.

原本O 係-2, 每粒O 多咗兩粒electron, 總共四粒;
依家同時放出四粒electron 俾四粒N 形成NO2, 自己氧化數變做0, 形成O2.
你講個case 即係一粒O 俾晒4粒electron, 然後同另一粒O 形成O2,
唔係冇可能, 不過要一次過嘔四粒? 仲要係O 甩電子?
真正情況冇人知, 不過直觀地去想就好.

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