M. Jika diketahui Ka asam asetat 2.10-5, maka pH larutan yang terbentuk
adalah….
A. 5- log 2
B.5
C.5+ log2
D. 9
E. 9 + log
9. Larutan CH3COOH 0,1 M, sebanyak 75 mL dicampur dengan 50 mL larutan NaOH 0,1
Jawaban:
Mmol CH3COOH= 75×0.1 = 7.5
Mmol NaOH. = 50×0.1 = 5
CH3COOH + NaOH —-> CH3COONa + OH-
m 7.5. 5
r. 5. 5. 5. –
———————————————————–
2.5. 0. 5
[H+] = Ka x mmol asam/garamnya
= 2×10^-5 x 2.5/5
= 2×10^-5 x 0.5
= 1×10^-5
pH = – log[H+]
= – log[1×10^-5]
= 5