A 20.0 mL of 0.27 M solution of the salt NaA has a pH of 8.70.
1 answer:
Answer:
a) 3.969
b) 3.489
Explanation:
a) Calculate the pk, value of the acid HA
PH of salt hydrolysis
P = 1/2 ( pkw + pka + logC )
8.7 * 2 = 14 + log ( 0.27 ) + Pka
∴ Pka = 3.9686 ≈ 3.969
b) Calculate the PH of a solution containing 0.3 M HA and 0.1 M NaA
PH = Pka + log ( salt / acid )
= 3.9686 + log ( 0.1 / 0.3 )
= 3.9686 - 0.48 = 3.489
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2) So, one alkyl group is CH3 and second one can be CH or CH2.
3) If we know that ratio between two types of hydrogens is 3:2, it can be concluded that second alkyl group is CH2.
4) Finally, we don't have any other signals and it indicates that part of the compound which continues on CH2 is exactly the same as the first part.
The ratio remains the same, 3:2 ie 6:4
