H2O

[物理小子]

my friend says that By detecting the pH of water, the pH7 tells that there is 10^7 H+ ions in 10^7 water molecules
therefore, 1 H2O is ionized into 1H+ and 1OH-

[johnsonlee]

chem 剛教到e度 H+ ions 係決定幾acidic OH- ions 係決定幾alkaline

[Wah!!]

my friend says that By detecting the pH of water, the pH7 tells that there is 10^7 H+ ions in 10^7 water molecules
therefore, 1 H2O is ionized into 1H+ and 1OH-

似乎唔可以用上"therefore"呢...
因為第一句唔會知道 OH- 是否存在.

[扒飯撈麵]

剛記起
in water 其實是
2H2O-H3O+ + OH-
一般會簡化成H+&OH-
詳情請向最少有AL chem或以上程度朋友請教

[o0oSkywalkero0o]

不妨搵下關於electronegativity o既information 可能會解答到個問題~~

[卷機山花]

睇黎水入面唔會存在O2-...
例如CaO掉落水唔出Ca2+同O2-而係Ca2+同OH-
但係點解呀？唔通O2-會傾向同水入面既H+黏返做OH- ？

[物理小子]

睇黎水入面唔會存在O2-...
例如CaO掉落水唔出Ca2+同O2-而係Ca2+同OH-
但係點解呀？唔通O2-會傾向同水入面既H+黏返做OH- ？

請況類似啦
啱啱學左半年到既AL Chem，似乎有少少眉目
Oxygen既First EA係-141 kJ mol^-1
但係佢既Second EA就有成+791kJ mol^-1
由放Energy變勁吸Energy
原因係叫佢食多粒電子實在難
咁細粒既Oxygen叫佢hold住兩個負charge會令佢既Charge Density好高
所以要有O^2-既ion會好難
但係OH^-唔同
佢變Octet係靠同1粒Hydrogen form covalent bond，即使係佢既electronegativity高，扯住粒Hydrogen既電子，佢既net charge都只係-(1+delta)
而唔係-2
低左好多亦穩定得多……

[Wah!!]

我想知道, 什么情況會有 O^2- 離子出現呀?

[扒飯撈麵]

in a overall reaction, when other part/ step of the reaction release energy more than the 2nd EA of O, O2- formation is engertic possible.
eg some metal like Na, Mg have 1st IE more than 1000kJ/mol. they are easily form oxide

[Wah!!]

我意思係游離的氧離子, 會唔會有可能出現呢???

[物理小子]

我意思係游離的氧離子, 會唔會有可能出現呢???

有……你要整梗整到既
真空既container中放粒Oxygen atom係度再打兩粒極高速既電子比佢囉
Enthalpy Change will be the sum of: Heat of atomization of 1/2O2(g), 1st EA of O and 2nd EA of O

[simonii]

正如skywalker 所說, 這是electronegativity 的問題
主要只有OH- 沒有是O2-在常態下會非常不穩定, 而且O對於H 來完是非常之bulky
所以O2- 的想法不是有錯, 但要知道一有O2- 出現的時候就很快便和H+ 合成OH-
結果就是絕大多數在電解水中的O2- 都變成OH-, 一個比較穩定的form

[少爺]

O2- + H2O --->2OH-
O2- is very unstable in aqueous form, due to the high charge density.