回應(會考化學)

回應1

pele159:

1. 請問 HCl(aq) & HCl(g)係咪compound ?

2. 地球最多的 element 係咪 oxygen ??地球最多的 metal咪 Iron ??

3. conc.H2SO4 + heat 係咪react cu ?Iron heat conc.H2SO4 係會出咩呀 ??

4. 係咪只有HNO3 stored in brown bottles ?

5. 其實而家應該做出面練習的mock 定係 redo 錯嘅野,溫下書好呀 ??

化學友:
1. HCl係covalent compound， (aq)同埋(g)只係代表唔同嘅states。

2. 地球最多嘅 element 係oxygen(之前寫錯,多謝網友指正)。地球最多嘅 metal係 aluminium。

3. Cu + 2H2SO4 --> CuSO4 + SO2 + 2H2O

Iron heat conc.H2SO4:
Fe + 2H2SO4 --> FeSO4 + SO2 + 2H2O

4. 除咗HNO3, 仲有AgNO3同埋KMnO4。CE chem大約知咁多就得o架喇

5. 化學友覺得你應該redo錯嘅野喇，同埋溫番dnote，唔好剩係做題目，會更有效。

回應2

pele159:
1. 86 Q.2The melting points of diamond, sodium chloride and potassium increase in the order:
A. diamond, sodium chloride, potassium
B. potassium, sodium chloride, diamond
C. sodium chloride, diamond, potassium
D. sodium chloride, potassium, diamond

請問 Metallic bond 和 ionic bond , 邊果melting points 大 d 呀 ?

2. 86 Q.38Bromine exists in two isotopic forms, 3579Br and 3581Br . The relative atomic mass of bromine is79.9. Which of the following statements is/are correct?

(1) The relative abundance of each isotopic form is about the same.
(2) The two isotopes have different numbers of protons.
(3) The two isotopes have different numbers of neutrons.
A. (2) only
B. (3) only
C. (1) and (2) only
D. (1) and (3) only

請問(1)點解arm 呀 ?

3. 87 Q.32(1) Nitrogen does not react readily with other elements or compounds.
(2) The outermost electron shell of the nitrogen atom is completely filled.

點解(1) 係arm 呀 ?? 乜Nitrogen 唔係covalent bond ?? 如果要does not react readily with other , 乜唔係 Noble gas 果d咩 ??

化學友:
1. 一般o黎講ionic bond強過metallic bond。所以ionic compound 嘅melting point 係高過metal。

2. 其實當年marking係錯o架。因為79Br有55%而81Br有45%，所以relative abundance is not about the same。

3. nitrogen(N2)內有nitrogen-nitrogen triple bond。化學反應時，需要好高energy才可以break nitrogen-nitrogen triple bond，所以佢係好少reaction，好unreactive。但係佢都有reaction嘅，例如: 3Mg + N2 à Mg3N2。

當然noble gases比N2 unreactive得多啦。

回應3

carmenlee:
你好，我有個chem既問題想問下OCl-會turn red litmus paper blue then white啦;咁H2SO3 turn完blue litmus paper red之後會唔會turn white?p.s.我見d solution都冇寫佢會turn white，但係SO3 2-唔係都bleach到野架咩?

化學友:
carmenlee，你係correct o架。但係SO32-嘅bleaching power比較mild，要long time先可以turn litmus paper white，所以ans只係寫即時observation。

回應4

sinying:
我想問下呢:alkonal加Na,CH3COOH加Na係唔係會都出H2??我睇書話佢地都係會出OH- ion,所以有H2放但咩唔係只係H+ion加Na先會出H2咩?OH-加Na為何出H2,而且CH3COOH唔係ACID來的嗎?咩唔係會出H+...........THX

化學友:
係呀，佢地會出H2 o架:

2CH3CH2OH + 2Na --> 2CH3CH2ONa + H2

2CH3COOH + 2Na --> 2CH3COONa + H2

sinying，化學友唸你睇錯o野喇。凡親一隻compound有H+或者hydroxyl group(-OH group 唔係OH- ion)就可以同Na react to give H2 o架啦。CH3CH2OH有 -OH group而CH3COOH有H+，所以有reaction。