cal pH include pressure

2009-08-06 4:50 am

Calculate the Ph of the following aqueous solutions prepared by adding 3.0L HBr (g), measured at 27C, 757 mmHg pressure, to sufficient water to give 0.10L of solution.

I really have no idea about how to calculate it, please help me, the answer is -0.08.

please show your answer steps by steps, thanks!!!

回答 (1)

老爺子

2009-08-06 8:18 am

✔ 最佳答案

Firstly, use ideal gas law to calculate the number of moles of HBr:

Pressure P = 757 mmHg = 757/760 atm
Volume V = 3.0 L
Gas constant R = 0.082 atm L mol-1 K-1
Temperature T = 27oC = (273 + 27) K = 300 K
No. of moles n = ? mol

PV = nRT
(757/760)(3.0) = n(0.082)(300)
n = 0.121 mol

After dissolve in water:
Molarity of HBr = 0.121/0.1 = 1.21 M

In aqueous solution, HBr is completely ionized in water to form H+(aq) ions.
Molarity of H+(aq), [H+] = 1.21 M
pH of the solution = -log[H+] = -log(1.21) = -0.08

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