1. 1 mole of NH3(aq) reacts completely with 1 mole of HCl(aq) (if I'm not mistaken), but can 100 cm3 of 0.1 M HN3 (aq) reacts complete with 0.01 mole of HCL (aq)? Since NH3 is a weak alkali and cannot fully ionize, therefore the actual amount of HN3 should be less than 0.01 mole. Is there any misconception in this statement?
2. Why some salts react with certain acids but not other type of acids? Is it related to the acidic / alkaline /neutral nature of the salts?
3. Do any two soluble salts react with each other (if I don't care about the products) ?
thanks
chem neutralization 問題(urgent)
2011-04-12 3:11 am
回答 (2)
2011-04-12 4:40 am
✔ 最佳答案
1. Typing mistake? HN3? I think it should be NH3...In fact, according to the below chemical equation:
NH3 + HCl ---> NH4Cl
mole ratio between NH3 and HCl = 1:1
No. of moles of 0.1M NH3 = 0.1*100/1000 = 0.01 mol
No. of moles of HCl = 0.01 mol
So they can completely react with each other, NO MATTER weak acid/base is used. Although weak acid/base ionize slightly to give H+/OH-, the loss of H+/OH- that reacted with other strong acid/base has to be compensated by ionizing more weak acid/base continuously. Thus, the reaction is finally complete if the no. of moles of acid and base used is suitable.
The above case only for weak acid/base + strong acid/base.
For weak acid + weak base, it involves some concepts about equilibrium taught in higher level, which involves complicated processes. And I don't mention it here.
2. Can you give some specific examples for reaction between some salts and certain types of acids?
3. Yes. Neutralization is one of the example.
But some do not react. If...
soluble salt (1) + soluble salt (2) ---> soluble salt (3) + soluble salt (4)
e.g. NaNO3(aq) + MgCl2(aq) ---> Mg(NO3)2(aq) + NaCl(aq)
(There is no precipitation.)
2011-04-12 19:23:18 補充：
It depends on the anion of the salt
for example in your example,
CO3^2- can react with acid to form carbon dioxide gas
Other example like
SO3^2- can liberate SO2 when reacted with acid
Some anion may be stable enough and not reactive to acid like SO4^2- and NO3-...
參考: Knowledge is power.
2011-04-14 9:57 am
2.
please think in this way:
H(+) may react with the anion, yielding respective acid:
sulphate + H(+) ----> H2SO4
sulphite + H(+) ----> H2SO3
carbonate + H(+) ----> H2CO3
chloride + H(+) ----> HCl
2011-04-14 01:59:28 補充：
H2SO4 and HCl is stable, so they'll not decompose;
H2SO3 and H2CO3 are unstable, which decompose into SO2 and CO2 respectively.
so the point is, see whether the possible compound formed is stable or not.
if stable, then no reaction;
2011-04-14 02:01:44 補充：
if unstable, then anion reacts with H(+), and further decomposes to respective compounds.
you've to learn what compounds are unstable, like carbonic acid, sulphurous acid, hypochlorous acid (in acidic medium), etc.
please think in this way:
H(+) may react with the anion, yielding respective acid:
sulphate + H(+) ----> H2SO4
sulphite + H(+) ----> H2SO3
carbonate + H(+) ----> H2CO3
chloride + H(+) ----> HCl
2011-04-14 01:59:28 補充：
H2SO4 and HCl is stable, so they'll not decompose;
H2SO3 and H2CO3 are unstable, which decompose into SO2 and CO2 respectively.
so the point is, see whether the possible compound formed is stable or not.
if stable, then no reaction;
2011-04-14 02:01:44 補充：
if unstable, then anion reacts with H(+), and further decomposes to respective compounds.
you've to learn what compounds are unstable, like carbonic acid, sulphurous acid, hypochlorous acid (in acidic medium), etc.
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