化學題目PH值計算

Molar mass of HCl = 1 + 35.5 = 36.5 g/mol

No. of moles of HCl = 15.8/36.5 = 0.433 mol

Volume of the solution = 400 ml = 0.4 L

Molarity of HCl = 0.433/0.4 = 1.08 M

Assume that HCl is completely ionized in water.
The amount of hydrogen ion contributed by the auto-ionization of water is negligible.
Molarity of H+(aq) ions, [H+] = 1.08 M

pH of the solution = -log(1.08) = -0.033


pOH = 14 - pH = 14 - (-0.033) = 14.033

[OH-] = (10)-14.033 = 9.27 x 10-15 M

Consider the auto-ionization of water.
H2O(l) ≒ H+(aq) + OH-(aq)
The auto-ionization of water contributes equal amounts of H+ and OH- ions.

[H+] contributed by the auto-ionization of water = 9.27 x 10-15 M

2009-07-18 14:15:55 補充：
No. of moles of [H^+] contributed by the auto-ionization of water
= (9.27 x 10^-5) x (400/1000)
= 3.71 x 10^-5 mol

The answer may slightly varies due to that different significant figures are taken in the calculation steps.

What's your concentration of HCl(l)？

2009-07-18 15:46:07 補充：
假設濃度是100%，這樣不是不合理嗎？照理說，100%的HCl應該是氯化氫氣體。