✔ 最佳答案
其實很簡單的呀。
只要學懂一條公式便可了。
pH= -log[H+]
0.1M HCl pH= - log(0.1)
= 1
1M HCl pH= - log(1)
=0
NaCl is neutral so whenever it is 1M or 0.1M the pH of it is 7
CH3COOH is a weak acid , the degree of dissociation of
H+ ion is low (ie. it is not complete dissociation) So we can not determine
the pH by this formula. Instead we should use the pH meter.
2011-10-23 22:36:42 補充:
先補充你再問O既問題, 12M HCl 的確用公式計到佢有negative pH value (ie. -1.08) negative pH value 絕對冇問題 (只限理論上)
不過~~~~~~~~
係實驗室裡面(或者正常環境裡面) ,係唔會度到有negative pH value. 原因是你常用的pH meter 果個electrode 係會唔多唔少受到強酸所影響(weak acid 唔會影響)
產生一個名叫acid error 的問題,會度到高左o既pH. 呢個問題暫時科學界都仲未有解決方法。
2011-10-23 22:37:02 補充:
而且,去到12M HCl 都算一隻好濃o既酸 咁濃O既環境 HCl 係做唔到
complete dissociation (因為太少水,dissociation effect 唔能夠完整咁樣進行,有D "H"依然同Cl covalent bond 緊) 所以 去到咁o既環境,"partial dissociation" direct apply the formula 係唔準。
2011-10-23 22:39:06 補充:
你用pH meter 會度到一個正數 你係唔知度究竟係H+ ion activities more than the degree of dissociation increased 定係調番轉。
總括來說,negative pH value is existed but you cannot show it concretely by nowadays chemical appartaus.
2011-10-23 22:39:12 補充:
PS. Ka (equilibrium constant) 會受好多因素影響,例如temperature 所以我地唔能夠用數字一概而論,我地只可以用pH meter 量度。
就算真係計到出黎,果個pH都只係某一個particular temperature o既pH.
2011-10-23 23:11:30 補充:
歡迎有問題再問,小弟定當盡力解答。