CHEM,,反應速率

ionic equation: 2H+(aq) + Mg(s) --> Mg2+(aq) + H2(g)

1) no
From the equation, rate of reaction depends on the concentration of H+(aq).
as ethanoic acid is a weak acid and only dissociates to liberate ionizable H+ in aqueous solution, 1M ethanoic acid gives <1M H+.
as H2SO4 is a dibasic strong acid, 1M H2SO4 dissociates completely to form 2M H+.
which is greater than that from ethanoic acid.
therefore, the rate of reaction of set (2) is higher than set (3).

2)compare the mole number of both reactants:
Mg:2.0/24.3=0.0823mol
HCl:1*0.1=0.1mol => 0.1mol H+
from the equation, the stoichemistric ratio, H+:Mg, should be =2:1
when all HCl, 0.1 mol is reacted, only 0.05 mol (< existed 0.0823mol) Mg is reacted.
Mg is in excess.

2007-04-30 15:52:22 補充：
1)反應速率與H 的濃度成正比CH3COOH只是弱酸,只有部分分子在水中離化產生H 因此 1M CH3COOH 只有 H (aq) HSO4-(aq) 完全離化HSO4-(aq) H (aq) SO42-(aq) 部分

2007-04-30 15:52:36 補充：
2)比較兩者摩爾數:Mg:2.0/24.3=0.0823molHCl:1*0.1=0.1mol 由2H (aq) Mg(s) --> Mg2 (aq) H2(g)反應物比例H (aq) : Mg(s) 為2:1只有0.05mol Mg與HCl反應HCl剩餘

2007-04-30 15:56:07 補充：
(此處和英文版有少許改動)相反, H2SO4是強酸,在水中完全離化,H 的濃度介乎1M到2M因為H2SO4(aq) -- H (aq) HSO4-(aq) 完全離化HSO4-(aq) H (aq) SO42-(aq) 部分H 在1M H2SO4的濃度比1M CH3COOH大反應速率較大