The maximum number of amino acid side chains that can potentially form an ionic bond ( - interaction) with the side chain of His is _at pH 2.1 ; ___at pH 7 and __at pH 11.5 and __at pH 13.5. (assume no partial charges, only /- whole number integers)

Abeaker with 2.00×102 ml of an acetic acid buffer with a ph of 5.000 is sitting on a benchtop. the total molarity of acid and conjugate base in this buffer is 0.100 m. a student adds 4.70 ml of a 0.360 m hcl solution to the beaker. how much will the ph change? the pka of acetic acid is 4.740.