化學 (科學) | fedest.com

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can help me to do this CHEM 問題

如題:
The mass of a sample of copper powder contaminated whit copper(2)oxide is known. Describe how you would conduct an experiment to determine the percentage by mass of copper powder in the sample. State the expected observation of the experiment.
(Hint: You may use an acid in the experiment)

P.S. 如可以告知小弟是何年HKCEE題和第幾題.

2007-03-19 16:03:30 · 2 個解答 · 發問者 Kelvin 1

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化學問題！！！(急)

1.Considering the law of conservation of mass, explain how rusted iron can weight more than iron.
2.Classify Bromine, Carbon and Sulphur into gas, liquids or solid at room temperature.

2007-03-19 15:21:37 · 3 個解答 · 發問者 ? 7

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電鍍 (硫酸銅鍍液分析) 步驟 (急)20點

分析硫酸銅內(氯離子)
請問分析步驟...?

如何配置0.0141N硝酸汞Hg(NO3)2溶液?

2007-03-19 14:40:19 · 3 個解答 · 發問者 ivy 1

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電子質子跟中子的關係

要做一份報告 !! 誰可以簡短的解釋給我這三者的關係
重量押 !! 什麼都好的 !!
拜託大家因為我真的搞不懂 ><
有英文版也OK !! 不要cope 或太長的唷 !!!!

2007-03-19 07:51:51 · 1 個解答 · 發問者 s503042001 5

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chem molarity

A sample of concentrated hychrochloric acid has a density of 1.21 g cm^-3 and contains 32.3% of hydrochloric acid by mass. What is the molarity of the hydrochloric acid in the sample?

2007-03-19 06:54:15 · 1 個解答 · 發問者 ? 2

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electron configuration of Pd

why does Pd have electrons in the 4d subshell but not in the 5s subshell?

2007-03-19 03:28:03 · 1 個解答 · 發問者心花 5

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這種橄欖皂配方做的成功嗎?

我想做一塊只有橄欖油+乳油木果的手工皂

橄欖油450g+乳油木50g(皂化價0.128)
180CC水
60g氫氧化鈉(約90%鹼化)
10ml香草香精

可以請高手幫我看, 這樣比例可以成功嗎?

我在知識找到乳油木的皂化價是0.128, 但是看到陳怡安的(好色香皂自己做)那本書寫0.137, 到底哪個才對阿?

我不小心到(extra virgin), 會影响皂化時間嗎? 因為已經買了不想浪費.....

2007-03-18 18:21:01 · 2 個解答 · 發問者 ? 2

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我想問................(plastic)

1) Does Nylon melt when it put in boiling water?
ANS:Nylon does not melt in water,
but burns and decompose when heated strongly.

我唔係好明乜唔係話themoplastic會soften when heated咩?
boiling water唔夠高溫

2007-03-18 18:05:53 · 2 個解答 · 發問者 chunfaat 2

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化學問題[石油及摩爾](超難)

1. 3.1g某水合碳酸鈉 Na2CO3 ．xH2O可與25.0cm^3的2.0M硝酸完全反應。x是多少??

2. 將煤油和苯乙烯回流加熱一段時間,再把液態生成物倒入甲醇中,生成透明無色固體。下列哪些陳述正確??
(1)反應是加成聚合作用
(2)煤油是催化劑
(3)該透明無色固體是一熱塑性塑膠

2007-03-18 17:38:21 · 3 個解答 · 發問者 STEVIE-G™ 7

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金屬中的化學鍵是不是很強?

如題...............................

2007-03-18 17:27:55 · 2 個解答 · 發問者可憐的混血王子 3

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1 gcm^3 = 幾多dm^3?

2007-03-18 05:35:07 · 1 個解答 · 發問者 ? 2

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邊度有小型電子磅買呀??

我要0.1克精度
$$100-200
最好近彩雲村啦

2007-03-17 14:44:52 · 1 個解答 · 發問者 ? 3

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Chem `

Use equations to explain the observation
1.when a few drops of copper(II) sulphate solution are added to the reagent in bottles dliute sodium hydroxide solution or duilte sulphuric acid, a pale blue precipitate forms.

2. When carbon dioxide is pass through the reagent in dilute sulphuric acid, a white precipitate forms.

THX~

2007-03-17 13:04:51 · 2 個解答 · 發問者 mandy 1

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用硫酸溶液做鋁陽極處理的反應式

請問鋁和硫酸(做電解液)在電化學製程時,陽極與陰極的反應式.最好能附上參考資料出處,感恩喔~

2007-03-17 12:23:19 · 1 個解答 · 發問者八寶冰沙 2

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R-CHOH-CH3 + I2, NaOH 會變咩?

R-CHOH-CH3 + I2 , NaOH
會變
[R-COO]- or [R-CHOHO]- ?

triiodomethane test

2007-03-16 20:53:54 · 2 個解答 · 發問者 mC 2

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我想問化學小問題...高手請進

請問什麼是C7H16的同分異構物?

我的問題大致上是這樣...謝謝
看課本也看不太懂的說= =

2007-03-16 16:21:15 · 4 個解答 · 發問者 Anonymous

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ethanoic acid

Which of the following particles is the smallest amount in a dilute aqueous solution of ethanoic acid?
A. CH3COOH
B. OH-
C. H+
D. CH3COO-
explain

2007-03-16 13:59:29 · 2 個解答 · 發問者 2003 2

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aluminium anodization

aluminium anodization會唔會increase the percentage of oxygen in a piece of aluminium?

2007-03-16 13:56:54 · 1 個解答 · 發問者 2003 2

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Form 4 Chemistry

The relative atomic mass of element X is 74.9. It forms an oxide containing 24.3% of oxygen by mass. What is the mole ratio of X to oxygen in the oxide?

[Steps please]

2007-03-15 18:16:45 · 1 個解答 · 發問者 ? 2

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一條有關化學反應質量既數

我唔識點做.
請幫忙.
pls give me the solution and ans.

1)消防人員使用的防毒面具逍常含有超氧化鉀(KO2)。超氧化鉀會與呼出空氣中的二氧化碳和水反應,生成氧氣:
4KO2(S)+2H2O(g)+4CO2(g)------->4KHCO3(s)+302(g)
假設一個人在20分鐘內呼出了14.0g的二氧化碳。
a)要完全與呼出的二氧化碳反應,防毒面具需含多少質量的超氧化鉀?
b)若上述反應的效應為80%,需含有的超氧化鉀的質量會是多少?
(相對原子質量:C=12.0,O=16.0,K=39.0

2007-03-15 17:36:57 · 2 個解答 · 發問者 ? 1

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FLAME TEST

FLAME test係唔係only test for ions??
element 得唔得架？？

2007-03-15 17:33:41 · 2 個解答 · 發問者 ? 1

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lattice

經常在書看lattice此字,是甚麼意思?

(Don't copy)

2007-03-15 17:21:10 · 2 個解答 · 發問者 2003 2

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甚麼co-ordination number?

甚麼co-ordination number?

(p.s冇放錯sub-topic)

2007-03-15 14:36:36 · 1 個解答 · 發問者 2003 2

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chemical properties

The chemical properties of an element depend on
A. the number of eletron shells in its atoms.
B. the number of outermost shell electrons in its atoms

whether A or B is correct?
From the answer of Joint-us,it is B
but my book said that the chemical properties of an element depend on electronic arrangement?

2007-03-15 14:33:52 · 3 個解答 · 發問者 2003 2

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FeS2.

Upon heating,a mixture of iron and sulphur gives a block substance.Which of the following statements concerning the black substance are correct?

(1) It is insoluble in water
(2) It can be attracted by bar magnet
(3) It reacts with dilute hydrchloric acid to give a gas with pungent smell.

Just explain (2)and(3)
All sulphide ore can react with acid?

2007-03-15 14:31:54 · 1 個解答 · 發問者 2003 2

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TAS--Comparison of rates of hydrolysis of Halogeno-compounds

1)ethanol + silver nitrate solution + 1-chlorobutane
2)ethanol + silver nitrate solution +1-bromobutane
3)ethanol + silver nitrate solution +2-bromobutane
4)ethanol + silver nitrate solution +2-bromo-2 methylpropane
5)ethanol + silver nitrate solution +bromobenzene
6)ethanol + silver nitrate solution +benzene

-->i wanna ask for the above chemical equations

As my school didn't teach it and I need to do this experiment.
Can anyone help me ?
Thank

2007-03-14 14:16:27 · 2 個解答 · 發問者 Anonymous

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