Question

When performing an experiment, you miss-calibrated your pH meter and all of the readings were 0.25 units higher than actual. How would this affect your calculated values for Ka? Provide a calculation to support your claim.

Answer 1

as we know kal acid constant) = (x² Where c is the concentration of weak electrolyte & X is the degree of dissociation derivation say the weak electrolyte is CH₃COOH CH3COOH 2 CHgcao" + H+ to c ca ca t=tc-ct where & is the degree of dissociation - then ka= [Chycoo] [ut] [a che cool] (ca) (C2) = (C2) (C2) c-ca C(1-2) then Cd² I-2 n For very weak electrolyte & (degree of dissociation) . is very small xo 1- 1 - Ka = ca a cat (x² = kay Now H+ = c = c ka viac . .- log ht = pH аѕ bел ещhion bH observed - p Hactual ł 0.25 cs Scamm login observed + log ini") car cubited = 0.25 CamScanner

log [* J actual = 0.25 Cut observed using ) log / Ska) actuala c l 0,25 ✓ Ka observed. C (Kajactual Jrkal abstined 0.25 Tabesteed' = lal antilong (0.25) (ka) actual (ka) observed (ka) actual 1= v (ka) observer 107782 squaring on the sides . (kal actual = (1.7782) (ka) observed u. (ka) actual (ka) observed = 1.177525 (Kg)observed a 0.316 x(ka) actual Thus when CPH observed is 0.25 more than (PH) actual they (ka) obsured will decreased by 00316 times then the actual (ka) Scanned with CamScanner