化學友,真係好唔該哂你呀!我明了,但係我又有問題.我想問呢preferentially discharge有好多個factor影響，其中一個係concertration la...好似CONC. NACL .Chloride ion 因為concertration高,所以唔係hydroxide ion preferentially discharge,而係Chloride ion.1.咁我想問點先算ion concertration高到可以preferentially discharge?有冇話大過某一個molarity 就會??2.decomposition of ionic compond:CaCO3會decompose,但係CuSO4,Na2CO3又唔會....Ammonium nitrate 會出N2O+H2O請問有咩方法可以知道 ionic compond會唔會decompose,仲有會產生d咩product?真係好唔該哂!!!
化學友:
1. sinying，化學友好多學生都會問e條問題，其實o向會考通常都冇指出molarity有幾高，但一定有明示比你睇，你好易就知答案。睇下e幾條CE題，你就明o架啦:
2005 Paper I 9
An experiment was carried out to study the electrolysis of a concentrated sodium chloride solution using several zinc-carbon cells as a source of electricity. The following diagram shows the set-up used:
(o拿e條一定出Cl2)
2001 Paper I 9
A student used the set-up shown below to prepare hydrogen and chlorine by electrolysis of a very dilute sodium chloride solution. Contrary to the student’s expectation, a colourless gas X instead of chlorine was liberated at the anode.
(i) What is X?
(e條一定出O2)
1997 Paper II 7
During the electrolysis of 1M copper(II) chloride solution using copper electrodes, which of the following changes would occur at the electrodes?
Cathode Anode
A. hydrogen liberated chlorine liberated
B. copper deposited chlorine liberated
C. copper dissolved copper deposited
D. copper deposited copper dissolved
(e條answer係D，1M代表conc.定dil.其實都唔影o向答案。)
2000 Paper II 5
Which of the following gases are the major products liberated in the electrolysis of concentrated sodium chloride solution using carbon electrodes?
Cathode Anode
A. hydrogen chlorine
B. chlorine hydrogen
C. hydrogen oxygen
D. oxygen hydrogen
(e條answer係A)
根本o向會考知唔知molarity都一定搵到answer，佢唔會陰你o架。明白嗎sinying?
2.sinying，其實好多ionic compounds會o向高溫下decompose，不過會考應該就只係要知e幾隻就得(按下放大):
仲有呀其他ionic compounds嘅decomposition o向CE chem係唔會要你自己寫，應該會好似下面咁，佢會將d reactants同埋products寫晒出o黎，要你將d文字寫成chemical equation。例如,
Ammonium nitrate decomposes under high temperature to give dinitrogen oxide and oxygen. Write the chemical equation for the reaction involved.
sinying，希望化學友嘅回應 幫到你啦。
2 則留言:
真係唔該哂,你個表好有用,我立即抄低了!
但係呢,我揾到一條ce mc:
26.On heating, blue copper(II) sulphate crystals gradually change to a white powder. Which of the following statements are correct?
(1)Heat would be liberated if water is added to the white powder.
(2)On further heating, the white powder would turn reddish-brown.
(3)chemical change occurs during the heating of the blue crystals.
A. (1) and (2) only
B. (1) and (3) only
C. (2) and (3) only
D. (1), (2) and (3)
answer話copper(II) sulphate唔會decomposition,我想問依d compond 係唔係要死記或者好冇方法記架?
再一次唔該哂!!
化學友我想問你關於chem個d colour.好似I2咁,係organic solvent係 purple,係佢gas state都係purple.重有無其他係有唔同colour係唔同state加.重有我想問sulphur,bromine,ammonia個d係room temperature係咩colour同邊d係denser than air...唔該哂!!!
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