幾條 F.4 chem,關於acid同中和作用

1.
dil. sulf. generally contains more ions than conc. sulf.
well, there're ions in conc. sulf., due to autoionization (or autoprotolysis or what):
2H2SO4 <======> H3SO4(+) + HSO4(-)
in fact conc. sulf. is a conductor of electricity.

however, i looked up the equilibrium constant of this reaction from Wikipedia,
K = 2.7E-4
and concentration of each ion is about 0.30M. with total ion concentration as 0.6M (considering 18M conc. sulf.).

well, the concentration of ions for conc. sulf. is quite significant, yet even 0.5M dil. sulf. has more ions than this.

2.
yes. they dissolve in water to give acidic solutions (carbonic acid; nitric acid and nitrous acid).

3.
same.
HNO3 + NaOH ------> NaNO3 + H2O
HNO3 + NH3 ------> NH4NO3
strength of bases do not vary the no. of mole of reagents needed for complete reactions.
as long as they're equimolar, complete reaction occurs (for acid-base reaction).

4.
as mentioned by Knowledge.
energy is needed (absorbed) for ionization of ammonia in rpoduction of ammonium ions. the overall heat realeased would be reduced.

5.
discard result of titration 1.
first calculate no. of mole of acid in the 25ml solution -- note the basicity of acid;
then calculate total no. of mole of acid used;
you have the mass and no of mole of acid, what else can't you get?

6.
yes.
pH = -log[H+]
pH = 0 when concentration of H(+) = 1M
theoretically, when concentration of proton is higher than 1M, pH can be negative.

it can be achieved by using higher concentration of REALLY strong acid, like hydrobromic acid, hydroiodic acid, perchloric acid, perioidc acid etc.

some "magic acid", composed of two or more chemicals, may also have this effect.
famous example is mixture of HF and SbF5, antimony pentafluoride:
HF + SbF5 ------> H(+) + SbF6(-)
the anion formed is a very veery weak base, making reverse reaction not possible. of course the medium of this reaction cannot be water.


2011-02-09 15:47:16 補充：
5.
yes, it's 195 g/mol.
remember the unit:
molar mass: g/mol
molecule mass: amu

Guess
3. Yes.
4. But the heat released is not equal. Some energy is used to ionize the ammonia molecule to give hydroxide for neutralization. So heat released of neut of weak base(acid) and strong acid(base) should be less than heat released of neut of strong acid and strong base.

LOK ：conc. sulphuric acid是難導電的,因為conc. sulphuric acid只有很少水,不足以將足夠的acid 變成mobile ions,是你自己調轉

1.點解dilute sulphuric acid既導電性能好勁過conc. sulphuric acid??
你係咪調轉咗呀？應該係conc. H2SO4嘅conductivity好過dil. H2SO4.

6.有負值

其他……得閑先計