化學

when going down the group , why the reactivity of elements increase ????????
please explain
thx

2007-03-13 18:48:18 · 2 個解答 · 發問者 彤彤 3

Fe2O3 AND Fe3O4 有咩分別

2007-03-13 17:53:20 · 2 個解答 · 發問者 ? 1

咩叫 anti-acid?
有冇 H+?

2007-03-13 16:43:32 · 2 個解答 · 發問者 Chiu Hung 1

超氧化鉀(KO2)會與呼出空氣中的CO2和H2O反應
生成氧氣：

4KO2(s) + 2H2O(g) +4CO2(g) ----> 4KHCO3(s) + 3O2(g)

假設一個人在20min內呼出14g的CO2。


a). 要與呼出的CO2完全反應,需要多少質量的KO2
b). 上述反應的效率為80%,需要的KO2質量會是多少



a我應該做得對
但b就不確定了
請列步驟
thx for help very much！！

2007-03-13 15:37:51 · 1 個解答 · 發問者 ching 2

有人話電芯冇晒電時會輕左，係唔係架？

2007-03-13 05:04:11 · 4 個解答 · 發問者 班戟小子 5

為什麼化學書中寫著原子是(g)..即氣體呢??
所有原子都是氣體ma??

2007-03-12 18:42:06 · 2 個解答 · 發問者 ? 2

A new herbicide- Herbigon is dissolved in 1 M acetic acid for technical reasons .Ksp of Herbigon = 8.10×10−6. The formula for Herbigon is X-acetate (where X= the cation of the salt that kills weeds) Since it is critical to have Herbigon dissolved, you are working on adjusting the pH so Herbigon will be soluble at the concentration needed to kill weeds. What pH must the solution have to yield a solution in which the concentration of X+ is 5.50×10−3M ? p-Ka of acetic acid = 4.76

2007-03-12 03:00:42 · 1 個解答 · 發問者 ? 1

The reaction below is catalyzed by hydrogen ions. It is found that the rate of the reaction depends only on the concentration of sucrose, for a given concentration of hydrogen ions.

C12H22O11 + H20 > C6H12O6 + C6H12O6

At 25 degree Celsius, when the initial concentration of sucrose was 1.00moldm^-3, the following data were obtained：

http://i75.photobucket.com/albums/i308/Tolland/chem.jpg

How would halving the initial concentration of sucrose affect the half life？

2007-03-11 19:21:48 · 1 個解答 · 發問者 David 1

請列出以下的化學式：
1乙烯
2聚乙烯
3單糖
4多糖
5氨基酸
6蛋白質

2007-03-11 17:21:37 · 2 個解答 · 發問者 Anonymous

以下鹽類的方法,同埋有關反應方程式...
(1)caso4
(2)mgso4
(3)nh4cl

2007-03-11 16:40:07 · 1 個解答 · 發問者 alan 2

以下鹽類的方法,同埋有關反應方程式...
(1)caso4
(2)mgso4
(3)nh4cl

2007-03-11 16:39:05 · 1 個解答 · 發問者 alan 2

wt metal oxides are soluble in water?
wt is the chemical equation between dilute ammonia solution and copper(II) sulphate solution?

2007-03-11 15:49:57 · 1 個解答 · 發問者 Silvia 1

有些地方不明

2H2SO4 + Mg ---->MgSO4 + 2SO2 + 2H2O

右邊6個O 左邊10個O
不明白為何已經平衡了
還是不是這樣數的



2Fe + 6H2SO4 ----> Fe2(SO4)3 + 3SO2 + 6H2O
請列一下步驟
thx！！

2007-03-11 15:04:08 · 1 個解答 · 發問者 ching 2

像是 1M g/cm3 的**水溶液

要算出他的莫爾 要怎麼解

我不是要正確答案 我是要怎麼解

好像是什麼 乘語 幾次方***.......

2007-03-11 13:41:43 · 2 個解答 · 發問者 Ｄｅｒｏｒ 1

我想問在稀酸中的兩枝碳電極上分別有咩物體.

2007-03-11 13:12:30 · 1 個解答 · 發問者 kint 1

我想問:

Given: H+ + OH- --->H2O enthalpy change = - 57kJmol^-1

calculate the enthalpy changes which would occur when the following solutions react as completely as possible:

(a)50cm3 of 0.01m Ca(OH)2 solution and 25cm3 of 0.01M HCl;
(b)50cm3 of 0.01m Ca(OH)2 solution and 100cm3 of 0.01M HCl;
(c)50cm3 of 0.01m Ca(OH)2 solution and 200cm3 of 0.01M HCl;

THX!~

2007-03-11 09:27:18 · 1 個解答 · 發問者 Yan Kit C 1

When HCI(g) dissovles into H2O(l), what can be found in the resulting solution?
為什麼我看答案時會出現OH-?
Acid 內是不是只有H+ and CI-?還是acid內有H+ , CI- and OH-, 只不過是H+的數量>OH-?

2007-03-10 08:50:39 · 1 個解答 · 發問者 kwan 6

唔一定要買
可以在邊度揾到
自製都得

2007-03-10 04:07:41 · 2 個解答 · 發問者 ? 3

火箭的燃料是什麼?涉及什麼化學反應?

2007-03-09 15:11:02 · 3 個解答 · 發問者 ? 1

我要急用呀，唔該你地幫忙．．．．．

2007-03-09 13:50:32 · 2 個解答 · 發問者 Anonymous

esterification入面,alkanol+ester,我本書講果d alkanol 果-OH group都係許最側邊,如果果-OH group許中間由product叫?
順便畫果strucutal formula黎睇睇...

thx

2007-03-09 10:59:34 · 2 個解答 · 發問者 2003 2

Is it possible to separate the isotopes of magnesium by chemical means?
Explain your answer.

2007-03-08 13:15:39 · 2 個解答 · 發問者 Anonymous

有人話鏹水係鹽酸(hydrochloric acid, HCl)和硝酸(nitric acid, HNO3)既混合物, 比例大約係3 : 1
有人話,鏹水既成份係濃硫酸(conc. sulphric acid)
咁究竟鏹水既成份係咩呀

2007-03-08 08:49:42 · 3 個解答 · 發問者 Yu Lai 2

5Br- + BrO3- + 6H+ ----- 3 Br2 + 3 H2O
C6H5OH + 3Br2 → C6H2Br3OH + 3HBr
When phenol is completely reacted, the free bromine formed will decolorize the methyl orange indicator.
After the solution changes to colorless,
why the solution turns to yellowish-brown precipitate
and have a nasty smell after a period of time?

2007-03-07 21:49:24 · 1 個解答 · 發問者 hello 3

10.0cm^3的2M酸溶液能與15.0cm^3的2M碳酸鉀溶液完全中和。該酸鹽基度是多少??

2007-03-07 18:42:37 · 2 個解答 · 發問者 STEVIE-G™ 7

用酒精來溶化油脂後, 是否油脂依然存在皮膚上 (或皮膚中)?

2007-03-07 13:14:17 · 1 個解答 · 發問者 Anonymous

I've got three relatively easy problems that I don't know how to solve...
Can someone explain it to me? thx
Q1...The pH of a weak acid solution is predicted by the approximate formula [H ] = squre root of (Ka * FHA). The predicted value of [H ] is found to be about 0.5% of FHA. Compared to the pH calculated, the true pH is (to two decimal places):
a) significantly higher
b) negligibly higher
c) significantly lower
d) negligibly lower <--- i think it's this one but i don't know how to explain/calculate it
Q2... The pH of 1.0 x 10-6 M NaOH (aq) lies between:
a) 7.96 and 8.00
b) 7.96 and 8.04
c) 8.04 and 8.10
d) 8.00 and 8.04
Q3... A weak acid is titrated with strong base. The pH is recorded one-third of the way to the equivalence point, then again two-thirds of the way to the equivalence point. The difference between the two pH values will be:
a) 0.30
b) 0.50
c) 0.60
d) 0.66

2007-03-07 09:46:15 · 3 個解答 · 發問者 Takuko 7

氨同銨有咩分別?英文係咩?

2007-03-07 07:53:06 · 3 個解答 · 發問者 Amethyst 2

因為家裡的拋光石英磚縫都黑黑的，有人說可以用工業用雙氧水，所以我想要找化工行，離新市或善化近的都ok，要確定有賣，才提供，因為之前的網友提供的地址，竟然是化工廠，根本就沒有賣，白跑一趟，麻煩各位網友提供一下，謝謝！

2007-03-07 05:22:44 · 1 個解答 · 發問者 葉子 1

mM怎麼換算成mg/Lㄚ??
有沒有簡便的公式呢?
還是這兩個單位是沒辦法換算的ㄚ?

2007-03-06 19:52:07 · 2 個解答 · 發問者 oboe05 2