A solution is prepared by adding 15.8g of HCl to enough wather to
make total volume of 400ml.What is the PH of the solution? How
much hydrogen ion is contribute by the auto-ionization of water?
- 老爺子Lv 71 decade agoFavorite Answer
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.
- 下雪Lv 71 decade ago
What's your concentration of HCl(l)？
2009-07-18 15:46:07 補充：