Which of the following aqueous solutions are good buffer systems? . 0.13 M potassium fluoride + 0.26 M hydrofluoric acid 0.16 M hydrocyanic acid + 0.15 M sodium cyanide 0.25 M hydrobromic acid + 0.20 M potassium bromide 0.30 M acetic acid + 0.22 M potassium acetate 0.28 M ammonium bromide + 0.38 M ammonia