## Chemistry (7th Edition)

$pH = 4.04$
1. Calculate the pKa Value $pKa = -log(Ka)$ $pKa = -log( 1.8 \times 10^{- 4})$ $pKa = 3.74$ 2. Using the Henderson–Hasselbalch equation: $pH = pKa + log(\frac{[Base]}{[Acid]})$ $pH = 3.74 + log(\frac{0.5}{0.25})$ $pH = 3.74 + log(2)$ $pH = 3.74 + 0.301$ $pH = 4.04$