點解寫ethanoate既formula 時,ethanoate 果part要寫係前面,metal 果part 要寫係後面ge? eg. CH3COOK 唔係 KCH3COO ge?同埋仲有咩野係好似ethanoate 咁要寫係前面ga?
2007-04-10 18:38:12 · 1 個解答 · 發問者 Jasmine 2 in 科學 ➔ 化學
In writing the formula of an ionic compound with a metal cation and an organic anion, write the organic anion first, and then the cation.
For example :
CH3COONa (sodium ethanoate)
C6H5OK (potassium phenoxide)
(HCOO)2Mg (magnesium methanoate)
CH3CH2OK (potassium ethoxide)
CH3CH2CH2CH2CH2CH2CH2COONa (sodium octanoate)
Reason :
An organic anion (e.g. CH3COO-) usually has a long formula, at least longer than that of a common inorganic anion (e.g. O2-).
Consider the sodium octanoate, the last example above.
When the formula is written as NaCH3CH2CH2CH2CH2CH2CH2COO, it is equivalent to Na+CH3CH2CH2CH2CH2CH2CH2COO-. It is not good to separate the +ve and -ve charges a long distance.
Therefore, it is written as CH3CH2CH2CH2CH2CH2CH2COONa,
which is equivalent to CH3CH2CH2CH2CH2CH2CH2COO-Na+.
2007-04-10 19:15:54 · answer #1 · answered by Uncle Michael 7 · 0⤊ 0⤋