2009-2-6 18:58
qwert123
中四化學......help~~~
第1-4題點做?.......
[url=http://uploads.bizhat.com/view/380989][img]http://s7.uploads.bizhat.com/0332c9c8/1_1_1.jpg[/img][/url]
[url=http://uploads.bizhat.com/view/380991][img]http://s7.uploads.bizhat.com/0332c9c8/2_1.jpg[/img][/url]
[url=http://uploads.bizhat.com/view/380993][img]http://s7.uploads.bizhat.com/0332c9c8/3.jpg[/img][/url]
[url=http://uploads.bizhat.com/view/380992][img]http://s7.uploads.bizhat.com/0332c9c8/4.jpg[/img][/url]
2009-2-6 20:27
昌昌
no.of moles of citric acid in 1000cm^3 = 8.06/192 = 0.042 mol
no.of moles of citric acid in 25cm^3 = 0.042 x 25/1000 = 1.05x10^-3 mol
no.of molesof NaOH 0.420 x (7.5/1000) = 3.15x 10^-3
3.15同1.05比較就得
ratio 3:1 (NaOH 1)
[[i] 本帖最後由 昌昌 於 2009-2-6 20:53 編輯 [/i]]
2009-2-6 20:50
昌昌
2. KOH既 moles = 0.5x20/1000 = 0.01mol
25cm^3既酸= 0.005mol (2元酸)
咁250cm^3既酸就有0.05mol
6.3/x = 0.05mol
x=126
WHERE X = MOLECULAR FORUMLA
3. methyl orange 黃-->紅
因alkali果陣係黃,完左果陣偏酸=紅
calculation
因為3個result冇個講寫trial
我拉晒3個平均=30cm^3
Na2CO3 + 2HCl --> H2O + CO2 + 2NaCl
睇到mol ratio HCl : Na2CO3 = 2:1
no.of moles of HCl = 2.0 x 30/1000 = 0.06mol
no.of moles of Na2CO3.XH2O = 0.03mol
106+18x = 0.3mol
x=1
[[i] 本帖最後由 昌昌 於 2009-2-6 20:53 編輯 [/i]]
2009-2-6 20:57
昌昌
no.of moles of HNO3 = 0.5x22/1000 =0.011mol
no.of moles of NaOH (當佢100%先) = 0.5/40 = 0.0125mol
ratio1比1
2個應該exactly至岩架
個difference就係impurity了~
0.0125入面得0.011先係NaOH
0.011/0.0125 X 100% =88%
仲有你D相係呢到睇就細到睇唔到
打開左就大到咩咁...下次影好D=.=
[[i] 本帖最後由 昌昌 於 2009-2-6 20:59 編輯 [/i]]
2009-2-6 23:02
magiyafeimo
做到野播,不過記住,體諒為主
2009-2-7 08:51
qwert123
[quote]原帖由 [i]昌昌[/i] 於 2009-2-6 20:50 發表 [url=http://www02.3boys2girls.com/redirect.php?goto=findpost&pid=32944899&ptid=540105][img]http://www02.3boys2girls.com/images/common/back.gif[/img][/url]
2. KOH既 moles = 0.5x20/1000 = 0.01mol
25cm^3既酸= 0.005mol (2元酸)
咁250cm^3既酸就有0.05mol
6.3/x = 0.05mol
x=126
WHERE X = MOLECULAR FORUMLA
3. methyl orange 黃-->紅
因alkali果陣係 ... [/quote]
Sorry,我唔係好明呢個部分:
[color=Red]106+18x = 0.3mol[/color]
x=1
2009-2-7 15:54
magiyafeimo
Na2CO3.xH2O係3.72g佢冇寫到
3.72g/0.03mol=molar mass=124
124=108+ (16 + 2)x
18=18x
x=1
2009-7-18 14:50
ZeroYip
ops>..
中文既問題真係唔明佢問咩...
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