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條題目係：
以下哪個反應會放出最多熱能？
A. 25cm^3 的 2M NaOH + 25cm^3 的2M HCl
B. 25cm^3 的 1M NaOH + 10cm^3 的1M H2SO4(硫酸)
C. 50cm^3 的 2M NaOH + 50cm^3 的2M HCl
D. 50cm^3 的 1M NaOH + 25cm^3 的2M H2SO4(硫酸)
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2007-03-23 2:10 am
回答 (2)
2007-03-23 2:31 am
✔ 最佳答案
要睇邊個放得最多熱, 就要知佢地既number of moles of H+ & OH-:H+ + OH- --> H2O
愈多mole reacted, more heat is given out.
A. number of moles of OH- = 2(25/1000) = 0.05 mol
number of moles of H+ = 2(25/1000) = 0.05 mol
so, 0.05 mol is reacted for A
B. number of moles of OH- = (25/1000) = 0.025 mol
number of moles of H+ = 2(1)(10/1000) = 0.02 mol
****因為H2SO4 is dibasic acid, H+ 要乘2
so, OH- is in excess, 0.02 mol is reacted for B
C. number of moles of OH- = 2(50/1000) = 0.1 mol
number of moles of H+ = 2(50/1000) = 0.1 mol
so, 0.1 mol is reacted for C
D. number of moles of OH- = (50/1000) = 0.05 mol
number of moles of H+ = 2(2)(25/1000) = 0.1 mol
****因為H2SO4 is dibasic acid, H+ 要乘2
so, H+ is in excess, 0.05 mol is reacted for D
overall, C reacted the most, C 會放出最多熱能
2007-03-23 2:29 am
其實唔使計ga bo,
只要比較邊個reaction produces最多H2O 就得ga la.
同埋要注意 佢地ge concentration. 2M 同埋 1M, 2M 比 1M 多一倍acid ions.
仲有 H2SO4 同 HCl ge分別, H2SO4 一個molecule有2個H+ ion 但係HCl 只有1個
所以 一個H2SO4 可以同NaOH react 2次, 出2 個水.
但係HCl 只可以同NaOH react 1次, 出1 個水
經過比較, 就可以得出 C) react得最多, 所以放出ge熱就最多la.
只要比較邊個reaction produces最多H2O 就得ga la.
同埋要注意 佢地ge concentration. 2M 同埋 1M, 2M 比 1M 多一倍acid ions.
仲有 H2SO4 同 HCl ge分別, H2SO4 一個molecule有2個H+ ion 但係HCl 只有1個
所以 一個H2SO4 可以同NaOH react 2次, 出2 個水.
但係HCl 只可以同NaOH react 1次, 出1 個水
經過比較, 就可以得出 C) react得最多, 所以放出ge熱就最多la.
參考: 自己
收錄日期: 2021-04-13 18:24:04
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20070322000051KK02639