chem strengths of acids

Thestatement is incorrect.
敘述句錯誤。

The concentration of hydrogen ions in a solution of an acid depends on not onlythe strength of the acid, but also the concentration of the acid. A moreconcentrated solution of a weaker acid may have a lower pH than a lessconcentrated solution of a stronger acid.
酸溶液中的氫離子濃度不僅受酸的強度影響，還受到濃度的影響。濃度較高的較弱酸溶液的 pH 可能低於濃度較低的較強酸溶液。

For example,
HCl is a strong acid, while CH3COOH is a weak acid.
pH of 0.001 M HCl = 3
pH of 1 M CH3COOH = 2.4

2014-08-07 21:15:23 補充：
acid molecules 在水中產生 hydrogen ions，稱為 dissociation (離解) 或 ionization (電離)，而不稱為 decomposition (分解)。

CH3COOH 是弱酸，在水中 partly ionized to give hydrogen ions.
CH3COOH(aq) ⇌ CH3COO⁻(aq) + H⁺(aq)

H2SO4 是強酸，現階段可當作在水中 completely ionized to give hydrogen ions.
H2SO4(aq) → SO4²⁻(aq) + 2H⁺(aq)

2014-08-07 21:16:23 補充：
計算弱酸水溶液的 pH，這是較高班才會學到，現階段無需學習。

2014-08-08 14:33:00 補充：
忘了回答你：

hydrogen ion 的 formula 是 H⁺，是由一個 H 原子組成的 positive ions。
acids 會 dissociate 出 hydrogen ions。

hydroxide ion 的 formula 是 OH⁻，是由一個 O 原子和一個 H 原子組成的 negative ions。
alkali 會 dissociate 出 hydroxide ions。

2014-08-08 14:35:48 補充：
不懂計算，就用我回答的那段文字便可以了：

"The concentration of hydrogen ions in a solution of an acid depends on not only the strength of the acid, but also the concentration of the acid. A more concentrated solution of a weaker acid may have a lower pH than a less concentrated solution of a stronger acid."

2014-08-08 14:40:35 補充：
若果真要舉例。

pH of 0.001 M HCl = -log(0.001) = 3 是你懂得計的。

pH of 1 M CH3COOH = 2.4 在網上可以查得，只需搜尋 "ph of 1 m ch3cooh" 便可。

First, what is pH ?
1.pH= concentration of hydrogen ions
2.concentration=mole of solute/volume

An acid will ionize to form H+ when dissolved in water.
Strong acid is an acid which completely dissociate(ionize) to form H+.
Weak acid is an acid which only partially dissociate(ionize) to form H+.
ie.some weak acid molecules do not form H+.

如果1個solution 得1滴strong acid 同一大兜水,入面H+ 既concentration會好低,咁pH都唔會好acidic
如果1個solution 有100滴weak acid係同一大兜水,雖然唔係每個acid molecule都會分出H+,但H+分出黎既總數都多過個1滴strong acid所分出黎既.


係同一volume(水)下,多d H+既數量,自然H+既concentration都會較高,所以1兜strong acid solution既pH唔一定低過weak acid solution.需要視乎(有幾多)acid,(有幾多)水,如果有相同咁多mole既acid,同樣volume既水,acid有同樣既basicity,strong acid solution的pH就會低過weak acid.

2014-08-07 17:43:13 補充：
So,the statement is false