Which of the following aqueous solutions are good buffer systems?
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0.11 M sodium hydroxide + 0.30 M sodium bromide
0.33 M potassium chloride + 0.20 M calcium chloride
0.28 M nitric acid + 0.23 M sodium nitrate
0.31 M ammonia + 0.31 M calcium hydroxide
0.21 M hydrofluoric acid + 0.20 M potassium fluoride