Explain:
(a). Why is `K_2Cr_2O_7` generally preferred to `Na_2Cr_2O_7` in volumetric analysis?
(b). Which divalent metal ion has maximum paramagnetic character amount the first transition metals? Why?
(c). How the colour of `K_2Cr_2O_7` solution does depend on pH of the solution?

Options

A. `Na^(2) Cr_2 O_7` is hygroscopic while `K_2Cr_2O_7` is not
B. `K_2Cr_2O_7` is hygroscopic while `Na_2Cr_2O_7` is not
C. `K_2Cr_2O_7` is pure and `Na_2Cr_2O_7` is impure
D. None of the above

Answer

A

Explanation

`Na_2Cr_2O_7` is hygroscopic and can not be used as a primary standard in volumetric analysis