pH value問題!!

By definition,
pH = -log [H+], where [H+] is concentration of H+.
pOH = -log [OH-], where [OH-] is concentration of OH-.

1.
By definition, we can notice that [H+ o既concentration愈高,pH value就愈低].

2.
In aqueous solution, at 298K, [H+][OH-] = 1*10^(-14) dm^6 mol^-2.
pH + pOH = 14

In aqueous solution, there must exist both H+ and OH-.
[OH-] in NaOH solution > [OH-] in NH3 solution
pOH of NaOH solution < pOH of NH3 solution

So, [NH3 solution o既pH value會低過NaOH solution]

3.
HCl is strong acid. Its ionization power is close to 100%.
1M HCl, pH = 0
0.5M HCl, pH = 0.3

CH3COOH is weak acid. Its ionization power is small.
1M CH3COOH, pH > 0
0.5M CH3COOH, pH > 0.3

你講得無錯
pH value係用H+黎計
咁點解NaOH有pH value嫁呢
咁係因為 concentration of H+ ion 乘 concentration of OH- = 1*10^(-13) or 1*10^(-14)
咁樣
我地知道 concentration of OH- 就可以用le個關係黎計算出H+濃度從而計出pH value

至於HCl 同 CH3COOH果度
由於HCl係強酸 姐係佢個H+可以完全ionize
而CH3COOH係弱酸 姐係佢個H+唔可以完全ionize(約只有5%的H+可以ionize)
但係由於佢係加same volume的水
所以佢地pH變化就應該一樣的

1)NaOH solution點解都會有pH value???????

因為OH- o既concentration愈高,pH value就愈高。

2)咁點解NH3 solution o既pH value會低過NaOH solution o既??

你要講明係同concentration的NH3 solution 同NaOH solution.......
eg, 1M NH3 同 1M NaOH...
因為NH3係weak alkali, 只出一部份OH-[concentration of OH- <1M];
而NaOH係strong alkali, 可以出哂全部OH-[concentration of OH- =1M],

concentration of OH- in NH3 solution < concentration of OH- in NaOH solution

所以同concentration的NH3 solution o既pH value會低過NaOH solution。

3)一杯HCL solution加水...佢個pH值o既變化
同一杯CH3COOH solution加水 有咩分別?

其實同alkali一樣, acid都有分strong同weak,
以1M HCL 同 1M CH3COOH 為例......

HCl 係strong acid, 可以出哂全部H+ [concentration of H+ =1M];
CH3COOH 係weak acid, 只出一部份H+ [concentration of H+ <1M];

concentration of H+ in HCl solution >concentration of H+ in CH3COOH solution

所以1M HCl 既pH 就比1M CH3COOH 低.