中四化學......help~~~

第1-4題點做?.......

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[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]

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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]]

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]]

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]]

做到野播，不過記住，體諒為主

[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

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

ops>..
中文既問題真係唔明佢問咩...