Both N i 2+ and Cu 2+ are border line acids( According toPearsons theory of hard and soft acids and bases) H2O , NO3- and SO4 2- all are hard bases. According to the above theroy hard acid will prefer to combinewith hard base and soft acid will prefer to combine with sift baseand thus a more satble p[roduct will be obtained. The border line acids will prefer to combine with both Hardbase and soft bases equally. Solution Both N i 2+ and Cu 2+ are border line acids( According toPearsons theory of hard and soft acids and bases) H2O , NO3- and SO4 2- all are hard bases. According to the above theroy hard acid will prefer to combinewith hard base and soft acid will prefer to combine with sift baseand thus a more satble p[roduct will be obtained. The border line acids will prefer to combine with both Hardbase and soft bases equally..