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標題: [Chem] urgent!! [打印本頁]

作者: 041087 時間: 2011-5-21 04:52 PM 標題: urgent!!

Q6我唔係太識得分C同D既分別,同埋我唔明c part點解係A而唔係B!!!

Q7我計極都計唔到個答案！THE ANSWER IS C

lq既ei)我唔明點解A個答案係413-432=-19而唔係4X413-432=1220!
同埋B個答案點解係1671而唔係-19????

請高手指教！

[ 本帖最後由 041087 於 2011-5-21 06:53 PM 編輯 ]

作者: Simon 時間: 2011-5-21 07:34 PM

6c. For combustion, heat is needed. But in the equation, you don't know whether heat exists or not.

7. 麻煩你寫出你既steps

LQ
ai. 只係break 一個 C-H bond
b. 1671 ?

作者: 041087 時間: 2011-5-22 01:05 AM

引用:

原帖由 Simon 於 2011-5-21 07:34 PM 發表
6c. For combustion, heat is needed. But in the equation, you don't know whether heat exists or not.

7. 麻煩你寫出你既steps

LQ
ai. 只係break 一個 C-H bond
b. 1671 ?

lqi)A IS -19
B IS 1671
其實係點計嫁？？

作者: Simon 時間: 2011-5-22 01:09 AM 標題: 回覆 3# 041087 的帖子

enthalpy change: Energy used for bond breaking + Energy released by bond formation

作者: 041087 時間: 2011-5-22 01:11 AM

引用:

原帖由 Simon 於 2011-5-22 01:09 AM 發表
enthalpy change: Energy used for bond breaking + Energy released by bond formation

Q7 AS FOLLOW

作者: 041087 時間: 2011-5-22 01:12 AM

引用:

原帖由 Simon 於 2011-5-21 07:34 PM 發表
6c. For combustion, heat is needed. But in the equation, you don't know whether heat exists or not.

7. 麻煩你寫出你既steps

LQ
ai. 只係break 一個 C-H bond
b. 1671 ?

HOW ABOUT Q6A AND B?

作者: Simon 時間: 2011-5-22 01:13 AM 標題: 回覆 5# 041087 的帖子

1 式已錯
Standard enthalpy change of formation is the enthalpy change when one mole of substance
is formed by its constituent elements at standard state under standard condition.

作者: Simon 時間: 2011-5-22 01:15 AM 標題: 回覆 6# 041087 的帖子

http://en.wikipedia.org/wiki/Bond_enthalpy

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