An aqueous solution of fluoroacetic acid, CH2FCOOH\text{CH}_2\text{FCOOH}CH2FCOOH, is allowed to reach equilibrium at 298 K according to the equation:
CH2FCOOH(aq)⇌H+(aq)+CH2FCOO−(aq) \text{CH}_2\text{FCOOH(aq)} \rightleftharpoons \text{H}^+\text{(aq)} + \text{CH}_2\text{FCOO}^-\text{(aq)} CH2FCOOH(aq)⇌H+(aq)+CH2FCOO−(aq)At equilibrium, the concentration of undissociated fluoroacetic acid is [CH2FCOOH]=3.20×10−2 mol dm−3[\text{CH}_2\text{FCOOH}] = 3.20 \times 10^{-2}\text{ mol dm}^{-3}[CH2FCOOH]=3.20×10−2 mol dm−3 and the concentration of fluoroacetate ions is [CH2FCOO−]=8.40×10−3 mol dm−3[\text{CH}_2\text{FCOO}^-] = 8.40 \times 10^{-3}\text{ mol dm}^{-3}[CH2FCOO−]=8.40×10−3 mol dm−3.
What is the value of the acid dissociation constant, KaK_aKa, for fluoroacetic acid at 298 K?
2.63×10−12.63 \times 10^{-1}2.63×10−1
2.26×10−62.26 \times 10^{-6}2.26×10−6
2.21×10−32.21 \times 10^{-3}2.21×10−3
4.54×1024.54 \times 10^24.54×102
