Because the range of possible values for Ka spans many orders of magnitude, a more manageable constant, pKa is more frequently used, where pKa = −log10 Ka.
bɪkˈʌz ðə ɹˈeɪndʒ ʌv pˈɑːsᵻbəl vˈæljuːz fɔːɹ kˈɑː spˈænz mˈɛni ˈɔːɹdɚz ʌv mˈæɡnɪtˌuːd, ɐ mˈoːɹ mˈænɪdʒəbəl kˈɑːnstənt, pˈiː kˈɑː ɪz mˈoːɹ fɹˈiːkwəntli jˈuːzd, wˌɛɹ pˈiː kˈɑː ˈiːkwəlz mˈaɪnəs lˈɔɡ tˈɛn kˈɑː.