化學

請問乜野是成分元素？

2007-04-10 12:38:30 · 1 個解答 · 發問者 Snow 1

發粉含有固體的酸和碳酸氫鈉。人們製造麵包和蛋糕時,會加入發粉。
1. 發粉在製造麵包和蛋糕時有何用處?
2.利用化學方程式,解釋發粉的作用。

2007-04-10 12:38:23 · 1 個解答 · 發問者 家浩 1

冷氣為何有抽濕作用??

2007-04-10 12:14:44 · 1 個解答 · 發問者 聶風 2

for each of the folowing pairs of substances, suggest a simple chemical test to distinguish one substance from the other and state the expected observation( Flame test is not accepted)

a zinc nitrate and magnesium nitrate

- 如果我加入NaOH- into zinc nitrate and magnesium nitrate, 2者就會有white ppt. 啦~
咁如果再加入excess NaOH- zinc nitrate 係唔係會變成colourless?
咁如果再加入 excess NaOH- magnesium nitrate 係唔係都係white ppt.?

2007-04-10 09:53:17 · 1 個解答 · 發問者 ? 1

on complete combustion, a 3.41 g of compound (CxHyOz) produced 8.6 g of carbon dioxide and 1.51 g of water.WHAT IS The empirical formula of the compound .

HOW TO DO??????

2007-04-10 09:37:24 · 2 個解答 · 發問者 carolene 1

please help

Consider the reaction:
ICl(s)I(g) +Cl(g) △H= +210kJmol-1
Explain why this value of △H is not the same as that of the I---Cl bond enthalpy.


20 marks will be given to the best solution

2007-04-10 08:21:28 · 1 個解答 · 發問者 Wilson 2

please help....

1.Consider the reaction:
Ch4(g)+Cl2(g)  CH3Cl(g) +HCl(g)
a.
what bonds are broken and what bonds are formed?
b.
Calculate:
i. the energy required to break these bonds
ii. the energy released on forming the bonds
E(C---H)=415kJmol-1; E(Cl---Cl) = 242 kJmol-1; E(C---Cl) = 338 kJmol-1;
E(H---Cl)=431kJmol-1

2007-04-10 08:19:59 · 1 個解答 · 發問者 Wilson 2

Please help me to solve these questions

Using the values of standard enthalpy change of formation given calculate the values of△H for the following reactions:

a. the thermal decomposition of BaCO3
b. C2H6(g) +Br2(l)  C2H5Br(l)+ HBr(g)
c. C2H4(g) + H2O(l) C2H5OH(l)
d. TiCl4(l) +2Mg(s)  Ti(s)+2MgCl2(s)
e. SO3(l) + H2O(l) H2SO4(l)

Thanks!!
20 marks will be given to the best solution!!! Thanks very much!!!

2007-04-10 08:05:56 · 1 個解答 · 發問者 Wilson 2

1) 2AgNO3(aq) + CaCl2(aq) ---> 2AgCl (s) + Ca(NO3)2 (aq)

2) Na2CO3(aq) + CuSO4(aq) ---> CuCO3 (s) + Na2SO4(aq)

題目問2隻solution mix埋之後 邊pair會give a precipitate
咁以上2條equation都係correct ,有 precipitate

寫equation個陣...
2種solution mix埋之後 點分辨佢ge product 邊隻係solid邊隻係aq ???

2007-04-10 06:44:46 · 1 個解答 · 發問者 ? 3

E=MC 2 is?

please answer me!!!!!!!!!!!!!!!!!!!!!!!

2007-04-10 06:37:43 · 2 個解答 · 發問者 Ram2007 3

請問 氧化鋁陶瓷用在什麼產業跟設備中 功能又為何呢??
未來的發展性又能到什麼樣的地步呢?傳統行業跟科技行業都用的到嗎? 煩請解答 感謝萬分

2007-04-10 06:23:08 · 1 個解答 · 發問者 nancynonno 1

FIGURE 4. Trolox equivalent (TE) values of pooled plasma to which
different concentrations of ()-epigallocatechin (EGC), ()-epicatechin
(EC), ()-epigallocatechin-3-gallate (EGCG), ()-epicatechin-3-gallate
(ECG), or a mixture of the 4 flavanols were added (A) or to which the same
concentrations of the flavanols were added (B). Values are the mean (<+->SEM)
of 3 determinations per time point. Antioxidant activity was determined by
using the trolox equivalent antioxidant capacity assay, which measured the
reduction in the radical cation 2,2'-azinobis-(3-ethylbenzothiazoline-6-
sulfonic acid) diammonium salt.

2007-04-09 21:53:04 · 1 個解答 · 發問者 Stanley 1

FIGURE 2. Mean (<+->SEM) plasma total flavanol concentrations [sum of
plasma ()-epigallocatechin, ()-epicatechin, ()-epigallocatechin-3-
gallate, and ()-epicatechin-3-gallate concentrations] after the consumption
of green tea, black tea, or a green tea extract supplement by 28–30 healthy
subjects.


TABLE 3
Percentage of the total dose of ingested ()-epigallocatechin (EGC), ()-epicatechin (EC), ()-epigallocatechin-3-gallate (EGCG), and ()-epicatechin-
3-gallate (ECG) from green tea (GT), black tea (BT), and a green tea extract supplement (GTS) in plasma and urine1



1 All values are x<+->SEM; n = 28–30 participants in a randomized crossover design. Means in a row with different superscript letters are significantly
different, P < 0.05 (mixed-model ANOVA and Tukey’s method).

2007-04-09 21:46:47 · 1 個解答 · 發問者 Stanley 1

Flavanol content of green tea (GT), black tea (BT), and a green tea extract supplement (GTS) administered as a one-time dose1


1 All values are the x<+-> SD of 2 measurements. EGC, (-)-epigallocatechin; EC, (-)-epicatechin; EGCG, (-)-epigallocatechin gallate; ECG, (-)-
epicatechin gallate. The flavanol content was analyzed by using HPLC with a binary gradient and ultraviolet visible detection. Means in a row with different
superscript letters are significantly different, P <0.05 (mixed-model ANOVA and Tukey’s method).

2007-04-09 21:38:52 · 1 個解答 · 發問者 Stanley 1

1.點解sodium carbonate會係alkaline?
佢同acid反應唔係會有carbon dioxide出現架咩?

2.點先叫efferressence occurs?why有hydrogen only叫gas bubble
有carbon dioxide叫efferressence occurs?

3.calcium hydroxide係slightly soluble in water,咁叫係alkaline呀?

4.點解chem書成日都話pipette係25cm^3?

5.點解呢dilute acid，即係加左水係d acid到，點解the no.of mole of the solute會一樣呀?
點解唔會多左呢?因為多左水既molecules呀嘛?why??

2007-04-09 17:58:00 · 1 個解答 · 發問者 doremi 1

丙-1-醇的燃燒熱多少?

2007-04-09 14:51:49 · 1 個解答 · 發問者 ? 1

氯離子和氫離子之間是離子鍵
氯化氫氣體理應是離子化合物先係??
點解氯化氫氣體係共價化合物

2007-04-09 14:30:11 · 2 個解答 · 發問者 ? 2

第1族元素原子數目會從上而下遞增,咁即係話金屬鍵應該會越來越強,但點解熔點反而會遞減呢????

2007-04-09 14:05:44 · 1 個解答 · 發問者 STEVIE-G™ 7

聚酯係咪熱固性塑膠?

2007-04-09 13:59:11 · 1 個解答 · 發問者 STEVIE-G™ 7

this is the questions
100 cm cube of water were placed in a plastic beaker The temperature was 18.7 C. 16.6 g of solid potassium iodide were added and the temperature fell to 13.4 C.
(take the c of water be 4.18 J/g/C)

a.
In this experiment it is necessary to make the potassium iodide dissolve as quickly as possible. Explain why. How is this brought about?

2007-04-09 12:19:04 · 1 個解答 · 發問者 Wilson 2

ammoium hydroxide係唔係 soluble?

2007-04-09 10:03:22 · 2 個解答 · 發問者 Chiu Hung 1

1.is there any observable change when chlorine water is added to NaCl~

2.liquid air 有冇 hydrogen??

3.點解某補習名師話 CO2 唔會cause acid rain~??(今年明報mock)

4.how to prepare 1M of ethanoic acid~??

2007-04-09 08:07:54 · 2 個解答 · 發問者 chun yu 1

CH2=C-CH2CH3 +H2O
　　　　\\CH3
↑即係2-methyl-1-butene加水
會出ｄ咩呢？？
要IUPAC name同substitutive IUPAC name
唔該

2007-04-08 20:07:37 · 2 個解答 · 發問者 HauMing 1

Such as (aq), (l)........ What do they stand for? Cna you also list out all those nouns that are related to them? THX!

2007-04-08 10:38:46 · 2 個解答 · 發問者 A student 1

Is there any possibility of making hydrogen from alkali instead of in acid? Is it using ionic metal?

2007-04-08 09:56:17 · 2 個解答 · 發問者 A student 1

chemical calculations and qualitative analysis
Cheng and Chow
publisher: Wilson
我問了好幾間書局，但仍然找不著這本練習，有冇人知道邊度有得賣?
thanks!

2007-04-08 06:25:27 · 1 個解答 · 發問者 ? 1

what is the role of sodium hydroxide in saponification?
A reactant ? or a catalyst?

2007-04-07 19:02:52 · 2 個解答 · 發問者 Chiu Hung 1

請問一下各位大大
理化的化學物質鐵加上錳等於何物質?
其物質又有啥功用?
請問一下

2007-04-07 17:20:11 · 2 個解答 · 發問者 必差 3

A mixture of zinc sulphide and zinc oxide is heated. After strong heating for 30 mins, 0.52g of a gaseous product A is formed. The residue is then heated strongly with excess carbon. 0.7g of another gaseous product B is formed after the reaction is completed.
a) Identity the two gaseous products in the reactions involved
b)Write balanced equations for the reactions as described above
c)calculate the percentage by mass of zinc oxide in the mixture

2007-04-07 16:07:56 · 1 個解答 · 發問者 kaleung 2

問一下喔, 25度c時,10的負八次方M NaOH溶液之pH值為6.00 錯在哪裡呢

2007-04-07 11:57:27 · 6 個解答 · 發問者 ? 1