Which of the following is/are correct?Of the 3d4 species, Cr+2 is reducing while Mn3+ is oxidising in natureCobalt (II) is stable in aqueous solution. However, in the presence of certain complexing reagents it easily oxidisedThe ions with d1 configuration can easily lose one more electronNa2Cr2O7 is preferred over K2Cr2O7 in volumetric analysis

Of the 3d4 species, Cr+2 is reducing while Mn3+ is oxidising in nature: This statement is correct. Cr+2 can easily accept an electron to become Cr+3, hence it is reducing in nature. On the other hand, Mn3+ can easily lose an electron to become Mn2+, hence it is oxidising in nature.

Cobalt (II) is stable in aqueous solution. However, in the presence of certain complexing reagents it easily oxidised: This statement is also correct. Cobalt (II) is stable in aqueous solution because it has a completely filled d-orbital. However, in the presence of certain complexing reagents, it can lose electrons and get oxidised.

The ions with d1 configuration can easily lose one more electron: This statement is correct. The ions with d1 configuration have only one electron in the d-orbital. This electron can be easily removed, making these ions good reducing agents.

Na2Cr2O7 is preferred over K2Cr2O7 in volumetric analysis: This statement is incorrect. K2Cr2O7 is preferred over Na2Cr2O7 in volumetric analysis because it is more soluble in water and its solution is more stable.