The hydronium-ion concentration of a 0.050 M solution of a weak acid (HA) is 5.0
ID: 1066725 • Letter: T
Question
The hydronium-ion concentration of a 0.050 M solution of a weak acid (HA) is 5.0 times 10^-3 M. The acid-dissociation constant is 1.37 times 10^-4 at 25 degree C. What is the pH of this solution? 5.30. 3.86 0.071 2.30 1.30 What is the pressure of a 35.4-L gas sample containing 3.23 mol of gas at 25.2 degree C? (R = 0.0821 middot atm/(K middot mol), 1 atm = 760 torr) 3.40 times 10^2 mm Hg 2.23 mmHg 2.94 times 10^-3 mmHg 43 times 10^2 mmHg 1.70 times 10^3 What is the pH of a 0.075 M HClO_4 solution? 11 41 12.88 15.12 2.59 1.12Explanation / Answer
35) pH = - log [ H3O+]
= - log [ 5 x 10-3 ]
= 3 - log 5
= 3 - 0.698
= 2.30
36) Using Ideal gas Equation = PV = nRT
Where, P = pressure, V = Volume ( 35.4 L ), n = moles ( 3.23 ), R =gas constant, T = temp = 25.2o = 25.2 + 273 = 298.2 K
Putting these values in above equation,
P x 35.4 = 3.23 x 0.0821 x 298.2
P x 35.4 = 79.077
P = 79.077 / 35.4
P = 2.23 mmHg
37 )
pH = - log10 [ H+ ]
= -log 10 [ 0.075 ]
= 1.12
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