If 20ml of 0.1M Naoh is added to 30ml of 0.2m ch3cooh (ka=4.74) , the ph of the resulting solutions is
a) 4.44 b) 9.56. c) 5.04. d) 8.96
Answers
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If 20ml of 0.1M NaOH is added to 30ml of .0.2M ch3cooh apka=4.74,the pH of a resulting solution
1)4.44
2)9.56
3)8.96
4)9.26
one year ago
Answers : (1)
Number of gram equivalents(eq) = moles x acidity of a base (or bascity of an acid.)
Or
= Molarity x Volume in litres x acidity of a base (or bascity of an acid)
So,
Eq(NaOH) = 20/1000 x 0.1 x 1 = 0.002 eq
Eq(CH3COOH) = 30/1000 x0.2 x1 = 0.006 eq
That means acid = base. Hence a salt would be formed in the solution with total volume = 30 + 20 = 50 ml
The pH of a strong base weak acid salt solution =
7 + 0.5(pKa +logC) where C is concentration of salt
concentration of salt = eq/volume =1000 x 0.005/50
= 0.01
So
pH = 7 + 0.5(4.74 +log0.01)
pH = 7 + 1.37 = 8.37
But I am not so sure about the answer......sorry if I am wrong