[CHEM] acid-alkali 3 條問題

1.
NH3 + HCl → NH4Cl

Case 1:
The reaction occurs in an aqueous solution. The NH4Cl formed would dissolve in the aqueous solution.
NH3(aq) + HCl(aq) → NH4Cl(aq)

Case 2:
Both ammonia and hydrogen chloride are gaseous. Since there is no water to dissolve the NH4Cl formed, white fumes are produced which contain small solid particles of ammonium chloride.
NH3(g) + HCl(g) → NH4Cl(s)

Case 3:
The reaction occurs in a solution of organic solvent, e.g. methylbenzene. The NH4Cl formed is ionic and does not dissolve in the organic solvent. Therefore, a white precipitate of NH4Cl is formed.
NH3(org) + HCl(org) → NH4Cl(s)

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2.
Copper(II) ions in water can react with KOH solution to form a blue precipitate of copper(II) hydroxide.
Cu2+(aq) + 2OH-(aq) → Cu(OH)2(s)

CuO solid is insoluble in water, and it does not give any Cu2+(aq) to the solution. Therefore, no precipitate occurs.

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3. The answer is D.

A is incorrect.
No gas is formed in the reaction between CaO and HCl.
CaO(s) + 2HCl(aq) → CaCl­2(aq) + H2O(l)

B is incorrect.
CaCO3 is insoluble in water.

C is incorrect.
No gas is formed in the reaction between KOH and HCl.
KOH(aq) + HCl(aq) → KCl­(aq) + H2O(l)

D is correct.
K2CO3 solution is alkaline. At room temperature, the pH of 0.1 M K2CO3 is about 11.6.
K2CO3 reacts with HCl to give carbon dioxide gas.
K2CO3(aq) + 2HCl(aq) → 2KCl(aq) + H2O(l) + CO2(g)
.

1.
HCL(aq) NH3(aq)-->NH4CL(aq)

NH4Cl 的 stage symbol 是 (aq) ..5是(S)
因為佢會溶在nitrates..so是aq

2. KOH 同 CuO 冇反應..
雖然話alkli acid的中和有反應.
但是CuO是金屬..alkali只能同non-metal oxide reaction
eg.2NAOH(aq) CO2-->NA2CO3(aq) H2O(l)

3.
A white solid dissolves in water to give an alkaline solution.即是話個solid是dissolves咁一定5是group2呢.
所以得返KOH ,K2CO3.之前dissolve左之後 左HCL..
(KOH和K2CO3兩條equation)
KOH:
KOH(aq) HCL(aq)----KCL(aq) H2O(l)

K2CO3:
K2CO3(aq) 2HCL(aq)----2KCL(aq) H2O(l) CO2(g)

咁e 得返 K2CO3reacts with dil. HCl to give a gas..所是是K2CO3

5知岩5岩呀.@﹏@

2008-06-07 21:58:25 補充：
--&gt 和----等於『→』(Uncle Michael借來用用=])