An aqueous mixture is prepared by combining different volumes of various solutions, each of concentration 0.20 mol dm-3.
Which mixture forms a buffer solution?
25 cm325\text{ cm}^325 cm3 of 0.20 mol dm−30.20\text{ mol dm}^{-3}0.20 mol dm−3 ethanoic acid and 25 cm325\text{ cm}^325 cm3 of 0.20 mol dm−30.20\text{ mol dm}^{-3}0.20 mol dm−3 sodium hydroxide
50 cm350\text{ cm}^350 cm3 of 0.20 mol dm−30.20\text{ mol dm}^{-3}0.20 mol dm−3 ethanoic acid and 25 cm325\text{ cm}^325 cm3 of 0.20 mol dm−30.20\text{ mol dm}^{-3}0.20 mol dm−3 sodium hydroxide
25 cm325\text{ cm}^325 cm3 of 0.20 mol dm−30.20\text{ mol dm}^{-3}0.20 mol dm−3 hydrochloric acid and 50 cm350\text{ cm}^350 cm3 of 0.20 mol dm−30.20\text{ mol dm}^{-3}0.20 mol dm−3 sodium chloride
50 cm350\text{ cm}^350 cm3 of 0.20 mol dm−30.20\text{ mol dm}^{-3}0.20 mol dm−3 nitric acid and 25 cm325\text{ cm}^325 cm3 of 0.20 mol dm−30.20\text{ mol dm}^{-3}0.20 mol dm−3 ammonia
